Crédimus in unum Deum...

Fidem, quam corde crédimus, ore autem dicámus:Crédimus in unum Deum Patrem omnipoténtem, factórem caeli et terrae, visibílium ómnium et invisibílium Conditórem.

Et in unum Dóminum nostrum Jesum Christum, Fílium Dei Unigénitum, et ex Patre natum ante ómnia sæcula; Deum ex Deo, Lumen ex Lúmine. Deum verum ex Deo vero; natum non factum, Omoúsion Patri, hoc est, ejúsdem cum Patre substántiae; per quem ómnia facta sunt, quae in caelo, et quae in terra.
Qui propter nos hómines, et propter nostram salútem, descendit de caelis, et incarnátus est de Spíritu Sancto ex María Vírgine, et homo factus est. Passus sub Póntio Piláto, sepúltus, tértia die resurréxit, ascéndit ad caelos, sedet ad déxteram Dei Patris omnipoténtis. Inde ventúrus est judicáre vivos et mórtuos, cujus regni non erit finis.

Et in Spíritum Sanctum, Dóminum vivificatórem, et ex Patre et Fílio procedéntem. Cum Patre et Fílio adorándum et conglorificándum; qui locútus est per prophétas.
Et unam, sanctam, Cathólicam et Apostólicam Ecclésiam.
Confitémur unum baptísma in remissiónem peccatórum.
Expectámus resurrectiónem mortuórum, et vitam ventúri saeculi.
Amen.

Thus is the Creed in the Mozarabic Rite of Spain. One interesting thing that you'll notice first here is that the Mozarabic Creed was, and is recited in the first-person plural (Crédimus...confitémur...expectamus, 'We believe...we confess...we await') as was the case with the Coptic, Ethiopian, Chaldean, and Armenian liturgies. This is in contrast to other Eastern and Western rites where the pronoun is changed to the singular (Credo...confiteor...expecto). In this respect this version preserves the form adopted by the First Councils of Nicaea and Constantinople, which was in the plural.

Now this, of course predated ICEL's changing of the Roman version from the singular to the plural during translation of the text. ;)

Another variation you can see is the wording:

1.) ...visibílium ómnium et invisibílium Conditórem.
2.) Deum ex Deo, Lumen ex Lúmine, Deum verum ex Deo vero. 'God from God, light from light, true God from true God'; compare Roman Deum de Deo, etc. Notice that it also sports the 'God from God' clause that was not originally present in the Greek text.
3.) Natum, non factum (as opposed to the Roman genitum)
4.) Omoúsion Patri, hoc est, ejúsdem cum Patre substántiae. This version preserves the Greek ὁμοούσιον instead of translating it with terms such as consubstantialem, and provides with it an explanatory clause: 'Omousion to the Father, that is, of the same substance with the Father')
5.) Per quem ómnia facta sunt, quae in caelo, et quae in terra.
6.) Passus sub Póntio Piláto...Inde ventúrus est judicáre vivos et mórtuos. The wording of the text in this portion closely resembles the Latin version of the Apostles' Creed: 'He suffered under Pontius Pilate, was buried, rose again on the third day, ascended into heaven; sits at the right hand of God the Father Almighty. From thence He shall come to judge the living and the dead; whose kingdom shall have no end.'
7.) Dóminum vivificatórem (cf. Roman Dóminum et vivificántem)
8.) Et ex Patre et Fílio procedéntem: cum Patre et Fílio adorándum et conglorificándum... (cf. Roman Qui ex Patre Filióque procédit: qui cum Patre et Fílio simul adorátur et conglorificátur). Note the et Filio in place of the infamous Roman Filioque.

Yet another difference is the place it is recited at Mass: the Creed is recited well after the Post-Sanctus and the Post-Pridie (roughly corresponding to our Canon), just before the Our Father. At this time the Priest takes the consecrated Host on the paten, holds it over the uncovered chalice and and says, or sings (after a Dominus sit semper vobiscum): "The Faith we believe with the heart, let us then say with the mouth." (Fidem, quam corde credimus...) He then elevates the Host to show it to the people as the Creed is sung (hear it sung here and here).

According to Dom Fernand Cabrol (from The Mass of the Western Rites):

The Spanish were the first in the West to introduce the symbol of Nicea-Constantinople into the Mass. In the East the custom already existed, and in 568 Justinus the Younger made it a law. In 597 the Third Council of Toledo issued an edict: "Ut prius quam Dominica dicatur oratio, voce clara a populo" (symbolum Constantinopolitanum) "decantetur, quo fides vera," etc. This is a fresh example of the eagerness shown by the Spanish Bishops to follow the customs of Constantinople. From Spain the usage spread into Gaul; but Rome held out long, and only yielded in the eleventh century. The true place of this symbol is in the rite of Baptism and it is not an essential element of the Mass. The Gallican churches sang it after the Gospel, at the end of the Mass of the catechumens, and this too is the place given to it by Rome. Like the Greeks and Orientals, the Spanish, by putting it at the end of the Canon, before the "Pater," rather disturbed the general equilibrium of this part of the Mass; and, moreover, diminished accordingly the importance of the "Pater."

Let's turn to the et Filio clause (as I would dub it now). As many of you may know, the origin of the Filioque clause in the West is usually traced in the anti-Arian situation of seventh-century Iberia: the clause was placed there in an effort to combat Arianism which was widespread back then in Visigothic Spain by making the Son like the Father in all things.

It would seem that the original form that this controversial clause took (at least in the Spanish version), however, was et Filio. The text of the Creed as it is recited today can already be found in pretty much the same form, with minor variants in the text, in the minutes of the Third Council of Toledo of 589 (to which some trace the origins of this clause), down to the omousion Patri, though an et Filio within the text is obviously still absent.

ITEM SANCTA FIDES QUAM EXPOSUERUNT CL PATRES IN CONCILIO CONSTANTINOPOLITANO.

Credimus in unum Deum, Patrem omnipotentem, factorem caeli et terrae, visibilium omnium et invisibilium Conditorem.
Et in unum Dominum Iesum Christum, Filium Dei unigenitum, ex Patre natum ante omnia saecula. Deum ex Deo, lumen ex lumine, Deum verum, ex Deo vero. Natum non factum, homousion Patri, hoc est, eiusdem cum Patre substantiae. Per quem omnia facta sunt, quae in caelis et quae in terris sunt. Qui propter nostram salutem descendit, et incarnatus est de Spiritu Sancto, et Maria virgine. Homo factus, passus est sub Pontio Pilato, sepultus, tertia die resurrexit. Ascendit in caelos, sedet ad dexteram Patris. Iterum venturus in gloria iudicare vivos et mortuos: cuius regni non erit finis.
Et Spiritum Sanctum, Dominum et Vivificantem. Ex Patre procedentem, cum Patre et Filio adorandum et glorificandum: qui locutus est per prophetas. Unam, catholicam, atque apostolicam ecclesiam. Confitemur unum baptisma in remissionem peccatorum. Expectamus resurrectionem mortuorum, vitam futuri saeculi. Amen.

The genesis of the clause can be seen in the third anathema of that same council: "Quicumque Spiritum Sanctum non credit aut non crediderit a Patre et Filio procedere, eumque non dixerit coaeternum esse Patri et Filio et coessentialem, anathema sit." (Whoever does not believe in the Holy Spirit or does not believe that He proceeds from the Father and the Son, and does not declare that He is coeternal and coessential with the Father and the Son, let him be anathema.) But this is also hardly new: a century before the third Synod, a different confession of faith found in the First Council of Toledo in 400 already has the following clauses: Spiritum quoque esse Paraclitum, qui nec Pater sit ipse, nec Filius, sed a Patre Filioque procedens. Est ergo ingenitus Pater, genitus Filius, non genitus Paraclitus, sed a Patre Filioque procedens. Eventually, the next time the Nicene Creed was quoted (during the Eighth Council of Toledo in 653), it now carries the et Filio within the text itself:

Credimus in unum Deum, Patrem omnipotentem, factorem cęli et terrę, visibilium omnium et invisibilium Conditorem.
Et in unum Dominum Iesum Christum, Filium Dei unigenitum, ex Patre natum ante omnia secula. Deum ex Deo, lumen ex lumine, Deum verum ex Deo vero. Natum non factum, homousion Patri, hoc est, eiusdem cum Patre substantiae. Per ipsum omnia facta sunt, quae in cęlo et quae in terra. Qui propter nos et propter nostram salutem descendit, et incarnatus est de Spiritu Sancto, et Maria virgine. Homo factus et passus sub Pontio Pilato, ac sepultus, et tertia die resurrexit. Ascendit in cęlos, sedet ad dexteram Patris. Inde venturus in gloria, iudicare vivos et mortuos, cuius regni non erit finis.
Credimus et in Spiritum Sanctum et Vivificatorem, ex Patre et Filio procedentem, cum Patre et Filio adorandum et glorificandum, qui locutus est per prophetas.
Et unam, catholicam, atque apostolicam ecclesiam. Confitemur unum baptisma in remissionem peccatorum, expectamus resurrectionem mortuorum, et vitam futuri sęculi. Amen.

The Eleventh Council of Toledo (675) contained a lengthy confession of faith at its preamble. It says the following concerning the Holy Spirit:

Spiritum quoque Sanctum qui est tertia in Trinitate persona, unum atque aequalem cum Deo, Patre et Filio credimus esse deum, unius substantiae, unius quoque esse nature, non tamen genitum, vel creatum, sed ab utrisque procedentem amborum esse Spiritum. Hic etiam Spiritus Sanctus nec ingenitus nec genitus creditur, ne aut si ingenitum dixerimus duos Patres dicamus, aut si genitum duos Filios predicare monstremur. Qui tamen nec Patris tantum, nec Filii tantum, sed simul Patris et Filii, Spiritus dicitur, nec enim de Patre procedit in Filium, vel de Filio procedit ad sanctificandam creaturam, sed simul ab utrisque processisse monstratur, quia caritas sive sanctitas amborum esse agnoscitur. Hic igitur Spiritus Sanctus missus ab utrisque sicut Filius creditur, sed minor Patre et Filio non habetur, sicut filius propter adsumptam carnem minorem se Patre et Spiritu Sancto esse testatur.

We also believe that the Holy Spirit, the third person in the Trinity, is God, one and equal with God the Father and the Son, of one substance and of one nature, not, however, begotten nor created but proceeding from both, and that He is the Spirit of both. Of this Holy Spirit, we also believe that He is neither unbegotten nor begotten, for if we called Him unbegotten we would assert two Fathers, or if begotten, we would appear to preach two Sons. Yet He is called the Spirit not of the Father alone, nor of the Son alone, but of both Father and Son. For He does not proceed from the Father to the Son, nor from the Son to sanctify creatures, but He is shown to have proceeded from both at once, because He is known as the love or the sanctity of both. Hence we believe that the Holy Spirit is sent by both, as the Son is sent by the Father. But He is not less than the Father and the Son, in the way in which the Son, on account of the body which He has assumed, testifies that He is less than the Father and the Holy Spirit.