Count/Noncount Nouns

http://www.english-zone.com/grammar/noncount.html

http://www.eflnet.com/tutorials/countnoncount.php

http://a4esl.org/q/j/ck/ch-countnouns.html

http://fog.ccsf.edu/~lfried/grammar/articlestest.html

http://ajaja.paradoxinc.org/Basic/Grammar/CountAndNoncount.html

http://www.eflnet.com/grammar/countnouns.php

Determiners & Quantifiers

http://occawlonline.pearsoned.com/bookbind/pubbooks/brown_activities/chapter7/fillinblanks1/deluxe-content.html

http://web2.uvcs.uvic.ca/elc/studyzone/330/grammar/mass.htm

Articles

http://esl.about.com/library/beginner/blathe.htm

When NOT to use an article:

http://www.polseguera.com/freegrammar/articles.htm