Grammar on the Net

1. English for you: http://www.english-4u.de/grammar_exercises.htm

2. English Grammar Secrets: http://www.englishgrammarsecrets.com/

3. BBC Skillswise: http://www.bbc.co.uk/skillswise/words/grammar/

4. Guide to Grammar and Writing: http://grammar.ccc.commnet.edu/grammar/quiz_list.htm