In addition to Skills Bank and the Understanding and Using English Grammar software, there are many useful online grammar or writing exercises:
http://townsendpress.com/
Paragraph Exercises
Passive Voice Quiz 1
Passive Voice Quiz 2
Raiders of the Lost Ark Passive Voice Quiz
English Page Verb Tense Review and Quizzes
Mixed Grammar Practice a4esl
Mixed Grammar practice and Phrasal Verbs (usingenglish)
Dave's ESL Cafe Grammar and Adjective clauses (and more!)
