Links for writers:

Query Tracker
A directory of agents that you can use to find agents that represent what you write. They tell you what each agent wants in a query (just a query letter, a letter and the first page, etc.) You can track your submissions and find out about agent response times.

Society of Children’s Book Writers and Illustrators
A great organization to join if you write
for children or young adults.

Romance Writers of America
For those who write romance.

Young Adult chapter of RWA
Young Adult Special Interest Chapter.