I've always been a huge advocate of #WritersSupportingWriters, and over the years (before querying, during querying, and just for fun), I've landed on a number of websites that helped me during the stage I was in.
Features interviews on many of your favorite agents--new and seasoned.
A great place to track queries, query responses from agents (i.e, how long it takes to read a full, what their responses look like, other writer's experiences with said agent, ect.), and to find out where you're at in the queue!
Keep up on what projects agents and editors are buying! However, please note that this is a paid resource.
Find out what literary agents and editors are looking for! Also, follow the #MSWL tag on twitter to see what they're tweeting about, too.
Melanin In YA
Your go-to source for all things Black in the Traditional, Young Adult realm.