Here are some links to writing resources that I have found useful over the years.
Society of Children's Book Writers and Illustrators - A professional organization for authors and illustrators of books for young people. There are regional chapters as well, with opportunities for meet-ups, critique groups and conferences.
Authors Guild does work to advocate for the working author.
The 12x12 Challenge is a challenge for a monthly draft and revision. It includes discussion forums and critique opportunities.
Children's Book Council
American Library Association
Ann Whitford Paul's Writing Picture Books was the book that I found the most helpful as I started writing and then a gleaned so much more from it when I went back and re-read it later.
Stephen King's On Writing is geared toward writing for adults but I found much of it useful, inspiring and fun.
A list of books about writing for children would be incomplete without a mention of Jane Yolen and Take Joy
Writing with Pictures by Uri Shulevitz is also a great read.
Tara Lazar's Storystorm
Reading for Research Month
Lately there have been more and more ways to connect with other kidlit folks via Twitter. Some of my current favorites to follow are:
#PBChat was started by Justin Colon. There are Wednesday night Twitter chats on craft from 9-10pm and a mentorship program
#WWTS- Writing with the Stars started by Tara Luebbe
Debbi Ridpath Ohi @inkyelbows
Sub It Club blog and Facebook page
Jennifer Laughran gives and agent's point of view on Twitter also @literaticat
Jennifer March Soloway gives helpful writing tips on Twitter @marchsoloway
BookEnds Literary has a great blog full of pointers
Blogs are listed here, but they are all active on Twitter also.
All the Wonders
Children's Book Podcast by Matthew Winner
Falling Leaves and Whispering Pines through SCBWI
The Writers Loft
The Writing Barn