The SCBWI acts as a network for the exchange of knowledge between writers, illustrators, editors, publishers, agents, librarians, educators, booksellers and others involved with literature for young people.
The Children's Book Council, Inc. is the nonprofit trade association of publishers and packagers of trade books and related materials for children and young adults.
There is a lot of great information on this site. Be sure to check out the section, Getting your Book Published. There are three subsections:
Illustrator's Guide: This guide is a specialized directory of Children's Book Council (CBC) member publishers' guidelines for reviewing illustrators' artwork. Members were asked to indicate how illustrators might arrange to have their work seen, and to specify what materials they most frequently wish to see.
CBC Member List: The member list contains a list of publishers that belong to the CBC. The list also contains contact information and current submission information. This is a good place to find out who is currently accepting unsolicited manuscripts.