AgentQuery Connect is an invaluable resource to anyone attempting to craft the tricky and crucial collection of words known as the query letter. At AQ Connect, you can post your query letter on their forum and receive feedback from other writers in the same boat. Help out your fellow man by critiquing his or her letter and they’ll likely do the same–so far most responses I’ve received are kind but honest, intelligent, and very very helpful. I think my letter has come a long way, thanks to everyone’s suggestions, and more are always welcome. It’s also great for meeting other writers and seeing the type of stories they’re working on, a lot of great stuff out there.
There’s also a forum for synopsis critiques. Mine’s still a mess, it’s hard to write a linear plot synopsis for an absurdist book…
– Corin
A smart gal I heard speak at UCLA’s Literary Agent panel this past weekend: 
Corin Reyburn 