In my search for an agent for my middle grade novel, I came across some very useful sites that are loaded with information about literary agents. I hope you find them useful too.
The first list is specifically about agents that represent MG. The second list is more general and includes all agents.
Blogs by MG/YA Writers
(all have agent information and/or interviews)
Casey McCormick - Casey's blog hosts agent info pages organized by who they represent: PB, MG and YA. She updates the pages regularly to keep them current. Most useful resource I found so far. Each page includes a short bio, what the agent is looking for, what author they represent, links to interviews, and other useful information.
Jay Eckert - I've known Jay from my online critique group, and I knew he had a list of agents that represent MG and YA on his blog. I didn't need an agent yet back then, but now I do and I'm glad I know about his blog! He updates his list regularly and adds new agents as they come up. Each name is a link to the agent's website.
Mother. Write. (Repeat.) - Every time I searched for interviews for a particular agent, this site showed up in the top results. Over 60 agents were interviewed, and they are listed alphabetically by last name, making it easy to find one particular agent.
Middle Grade Ninja - Robert Kent interviewed over 30 agents, asking them each 7 questions. They are also listed alphabetically by last name. Sadly, he is no longer updating his blog, but the reviews that are there can still be useful.
(sites you really should visit before querying any agent)
Absolute Write - This is a very popular discussion board for writers, free to join. It may be useful to find out other people's experience with an agent before querying.
Predators and Editors - This site is a must if you're querying an agent that is new or not well-known. It verifies that agents are legit and trustworthy, and flags those that charge fees or that are not recommended, for one reason or another.
QueryTracker - This site holds general information about each agent and links to success stories (interviews with writers that often include the winning query). It also lets you keep track of what agent you queried, record what the response was, and save a copy of your query. In addition to all that, there is a discussion board where members talk about their querying experience with each agent.
AgentQuery - Similar to QueryTracker. I still have to look into that site.