Online English Lab at Purdue (OWL)
Information on the writing process, grammar and mechanics, ESL, and more, including writer's block.
Guide to Grammar and Writing (Capital Community College)
Practices, powerpoints, grammar poll, and "ask grammar."
Grassroots Online Assistance
This site goes with the Grassroots textbook. It has practices for chapter reviews and quizzes, Grammar Jam, ESL Corner, Live Links to other help sites, and help with writing stronger paragraphs and essays.