Also see Reference Materials

Style and Grammar Guides
MLA: Guide for Writing Research Papers
UCLA's Guide to Internet Use (e.g., evaluating sites)
Strunk & White's Elements of Style
Bartleby.com (reference materials, including some on-line literature)
Webster's Dictionary Online
Roget's Thesaurus Online
ESL Resources on the Web
Harvard Writing Program Writing Guides
Guides to Argument and Critical Thinking