The Writing conference, Inc.

http://www.writingconference.com/writing.htm

National Scholastic Press Association

http://www.studentpress.org/nspa/contests.html

Writing.Com

http://www.writing.com/?rfrc=google&rfrt=googleContest6&sp=1

Writing-World.com

http://www.writing-world.com/contests/index.shtml

firstwriter.com

http://www.firstwriter.com/competitions/

Letters about Literature

http://loc.gov/loc/cfbook/lal-participation.html