I've been researching agents and publishing for a long time. I'm not saying that to brag (I mean, really, it would be bragging to say "I tripped over this awesome agent and contract without knowing anything!" but that hasn't been my path). When I first started out, I didn't really think I had a chance, so I really did everything by the seat of my pants. I queried the first agent who came up in my google search for a literary agent.
No really. I'm lucky that it was an agent who popped up on my list, but it could have just as easily been a scammer. After sacrificing that novel on the altar of naivety, I got wise and started doing my research. I realize that many people already know about these resources, but I never know when someone is going to stumble across my blog. So if you're looking for information on agents and some bits of publishing, check out these links.
Shipping & Handling, a podcast by two agents. You can download their episodes here. Why do I think it's important? These two agents (Bridget Smith and Jennifer Udden) talk about books, publishing and craft. You can send in questions, and they might just answer those questions. I love that they talk about what they love about books, and it really gives us writers a glimpse into the agenting world.
Query Tracker is one of those great places where writers can comment on agents. It's not as good as some places with an iron clad moderation, but with a bit of common sense, you can probably figure out which agents have trouble. Admittedly, some times a writer is bitter and the comments go south fast. I suggest that you use your discretion when posting and believing others on open forums.
Michelle Hauck runs a set of interviews called query questions where she asks agents about some of the most commonly fretted over issues in querying. I find these interviews particularly useful because she straight up asks them about the questions that every writer has gone insane over.
Krista Van Dolzer has a whole slew of agent interviews, but these ones you should be careful with. Some of the interviews are pretty dated. They make an excellent starting point, but in some cases, the agents have moved or left the business. Be careful and always do a separate search on agents to find where they are now!
I feel like I can't have a link post without mentioning Absolute Write. I like absolute write, but in the comments on agents section, there tends to be a lot of meanies and trolls. I don't really know why, but the trolls are particularly vigorous around the agent threads. In other parts of Absolute Write, the writers are really great and super supportive--some of my favorite forums!--but like any city, there are parts of town that you should carry a flashlight when you go into.
And lastly, you should always check Preditors and Editors. Some of their stuff might not be up to date with the newer agents, but the newer agents should be from agencies listed and rated at P&E.
I think I'm going to call it there. There are tons and tons of resources, but those are a great set to get a writer started. Feel free to leave your favorites in the comments (yes, even you totally published and successful people of awesome!).