Essential Writing Websites
Purdue OWL
http://owl.english.purdue.edu/owl/
This Purdue University OWL (Online Writing Lab) offers a range of helpful and current writing advice.
Online Thesaurus
http://thesaurus.reference.com/
In addition to featuring an online thesaurus, this site offers a word-of-the-day, an article about the most "looked-up" words in 2005, and word puzzles and games.
The Elements of Style by William Strunk
http://www.bartleby.com/141/index.html
This writing guide classic is now available on the "Bartleby" (free books online) site.