Hertfordshire Spanish Circle
Here are some suggestions:
Nivel 1 - Regular verbs in the present tense
http://www.studyspanish.com/practice/tenven.htm
Nivel 2 - Regular verbs in the Preterite and Imperfect (past) tenses
http://www.studyspanish.com/practice/pret1.htm
http://www.studyspanish.com/practice/imp1.htm
http://www.studyspanish.com/practice/pretimp2.htm
Nivel 3 - Irregular verbs in the Preterite and Imperfect (past) tenses
http://www.studyspanish.com/practice/pret6.htm
http://www.studyspanish.com/practice/imp3.htm
http://www.studyspanish.com/practice/pretimp3.htm