A few sites that may prove helpful for writers:

Publishers Marketplace is by far the most influential web site on publishing. If you’re looking for an agent you must combine other information and evaluation you might have obtained from other good sources with the real situation in the marketplace that this site offers you through its Top Dealmakers feature and much more.

American Booksellers Association
American Society of Journalists and Authors
Arts & Letters Daily
AWP The Association of Writers & Writing Programs
The Barcelona Review
R.R. Bowker – Books in Print
Hachette Book Group
HarperCollins
Henry Holt
Hyperion Books
The LoftNational Writers Union
W. W. Norton & Company
Novelists, Inc.
Penguin Putnam
Poets & Writers
Publishers Marketplace (In our opinion this is the best single source for publishing information.)
Publishers WeeklyPublishing News Direct (Great Britain)
Random House
Readerville Magazine on lineSimon & SchusterSt. Martin’s PressThe Writers Guild of America
Written Voices