Note to readers: I originally published the article back in 2008 and have updated it a few times, most recently on June 13, 2012. This article primarily addresses self-publishing a print book, though many of the tips apply to e-books as well.
Project Gutenberg Self-Publishing - eBooks
Poetry & Writing Community - Writers-Network.com - The Online Creative Writing Site
Teaching Graphic Novels
Trigger Street Labs
We Like to Write - Social Networking for Writers & Bloggers
Writing and Publishing News, Marketing, E-Books—Authorlink.com
Screenwriting, Screenplay, and Screenplays from the Scriptologist.com Screenwriting Magazine