This verb conjugation site is a great review of the formation of the forms of the regular preterite forms as well as those with spelling changes, stem-changes, and irregular forms. All sections have links to verb conjugation practice.

Great lesson on the three irregular conjugations of the imperfect tense: ser, ir, and ver. A quiz at the end of the lesson tests the student's mastery of these three irregulars.

Excellent explanation of formal commands in Spanish that use the pronouns "usted" and "ustedes." Stem-changers and irregulars are included in this lesson. Ample examples illustrate the formation and use of formal commands. A quiz at the...

A very brief explanation of how to form the present participle for ar/er/ir verbs and later form the present progressive tense with the participle.

This grammar tutorial explains the formation of the past participle for ar/er/ir verbs as well as some irregular forms. A couple of examples are given to show the formation of the present perfect.