Agent Blogs are a great way to stalk possible agents and get a feel for their likes and dislikes. Plus invaluable information on the submission and publication process abounds on many of these sites. With the resources listed below (in no particular order), there are no more excuses for not understanding how the industry works.
Dystel & Goderich Literary Management [http://dglm.blogspot.com/] – D&G’s stable of agents take turns blogging about publishing issues. The agency is interested in a wide variety of commercial, literary, and nonfiction titles.
Getting Past the Gatekeeper [http://agencygatekeeper.blogspot.com/] – An anonymous agent, repping YA and select nonfiction, blogs about author-agent communication and manners and provides a great sense of what it’s like working for a boutique literary agency in New York.
Janet Reid, Literary Agent [http://www.jetreidliterary.blogspot.com/] – Of FinePrint Literary Management, Ms. Reid provides frank submission and publishing advice.
Kidlit.com [http://kidlit.com/] – Agent Mary Kole with the Andrea Brown Literary Agency provides frank advice on picture book, middle grade, and young adult publishing (most of which can be applied to other genres). She also did a series of novel beginning critiques in January 2010 - definitely worth a look.
Nathan Bransford – Literary Agent [http://blog.nathanbransford.com/] – If you don’t know who Mr. Bransford is, you must remedy this immediately. An author himself, he provides tons of submission advice, just started a new series called Page Critique Monday, and is increasingly recognized as a digital publishing futurist thanks to opinion pieces over at the Huffington Post.
Miss Snark [http://misssnark.blogspot.com/] – Now defunct, the blog still has a vast amount of advice buried in its archives. In particular, check out her posts labeled 'Crapometer' to see if various hopefuls' hooks, queries, first pages make her cut.
Pub Rants [http://pubrants.blogspot.com/] – This is another must. Agent Kristen Nelson of Nelson Literary provides oodles of manuscript submission advice and does a great job of deconstructing publishing contracts, which you don't see a lot of on other agent blogs.
Rachelle Gardner, Literary Agent [http://cba-ramblings.blogspot.com/] – An agent for WordServe Literary. Although she reps primarily Christian fiction and nonfiction projects, Ms. Gardner’s posts offer great advice and inspiration for writers of all stripes.
My criteria included agents I regularly follow and who's posts are consistently useful and interesting. But I KNOW there are more out there, so who have I missed? I will be posting this and other notable writing websites (as I get to them) in the "Writing Resources" sidebar. So stay tuned!