Here are two links to the AP English Section of the College Board.

Sample Questions, Writing Tips, Etc.

Even if you are not going to try the AP Exam this year or next, you should peruse these sites.  They could help you become a more sophisticated writer.

English Language and Composition:

http://apcentral.collegeboard.com/apc/members/exam/exam_questions/2001.html

English Literature and Composition:

http://apcentral.collegeboard.com/apc/members/exam/exam_information/2002.html

Here's a link to the Online Writing Lab at Purdue:

http://owl.english.purdue.edu/

Here's a link to the Guide to Grammar and Writing at Capital Community College:

http://grammar.ccc.commnet.edu/grammar/index.htm

Here's a link to a site dedicated to literary devices:

http://literary-devices.com/

PLATO: https://ple.platoweb.com/