Test your English:
http://www.world-english.org/test.htm
http://www.test-your-english-now.net/
http://www.test-my-english.com/
http://www.english-test.net/
http://www.transparent.com/tlquiz/proftest/english/tlengtest.htm
General:
http://www.englishclub.com/grammar/index.htm
http://www.usingenglish.com/glossary.html
http://www.learnenglish.org.uk/grammar_home_frame.html
http://grammar.ccc.commnet.edu/grammar/
http://www.bbc.co.uk/skillswise/words/grammar/
http://www.bbc.co.uk/worldservice/learningenglish/index.shtml
http://www.englishgrammar101.com/
http://englishplus.com/grammar/
http://www.manythings.org/e/grammar.html
http://www.english-at-home.com/
http://www.englishpage.com/
Tenses:
http://www.speakspeak.com/html/d10a000_english_grammar_structure_of_tenses.htm
http://www.efe.co.uk/homenses.htm
http://www.buzzin.net/english/tenses.htm
Difference between two/to/too:
http://www.quia.com/pop/1000.html
http://www.towson.edu/ows/too.htm
http://www.wsu.edu/~brians/errors/to.html
http://www.teachingandlearningresources.co.uk/homophones3.shtml
Difference between your/you're:
http://www.wsu.edu/~brians/errors/your.html
http://www.englisch-hilfen.de/en/words/you_are_your.htm
http://www.wikihow.com/Use-You're-and-Your
http://elc.polyu.edu.hk/cill/eap/2004/u5/setphrases.htm
http://www.learn-english-today.com/idioms/idioms_proverbs.html
German:
http://www.ego4u.com/
http://www.englisch-hilfen.de/
http://www.englisch-lernen-im-internet.de/
http://www.vocabulix.com/online/Lernen/Englisch
French:
http://www.anglaisfacile.com/
http://www.lapasserelle.com/sm/ang90mp3/indexa90-fr.html
http://www.e-anglais.com/
