The Society of Children's Book Writers & Illustrators, SCBWI.org
(For the New England chapter, go to nescbwi.org)The Graphic Artist's Guild, gag.org
The Author's Guild, authorsguild.org
The Picture Book Artist Association, picturebookartists.orgThe Horn Book Magazine; get a subscription, follow their blog, or sign up for their newsletter! hbook.com/Publisher's Weekly; check out their children's book reviews or get a subscription, publishersweekly.comIllustration Friday is a great place to see some fresh art, and get some good ideas! There is also a blog link on the site, illustrationfriday.comIt is also a good idea to join a critique group, or make your own!
If you want to be an author or illustrator, it is imperative that you learn as much as you can about the market, trends, publishing process, new releases, and book awards. These organizations will help you do just that!
I will keep the list updated as I find out more information!