Writing Forums I've found helpful:
Absolute Write Water Cooler - Lots of information to learn about publishers, agents, query writing, and the craft of writing itself.
Forward Motion Writers - Home of the Merry Go Round Blog Tour
Question about an agent or publisher? Check here: Writer's Beware and here: Agent Query
Also of interest: Query Shark - For help with getting that query written so it gets past the "meh" stage.
US Writing Magazines:
Science Fiction and Fantasy Writers of America
Romance Writers of America
Mystery Writers of America
Horror Writers Association
Maryland Writer's Association
St Mary's Chapter: http://stmaryscountymwa.wordpress.com/