See my post here:
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=381x184#201My husband and I have been learnging and using ASL with our 20 month old toddler who is still mostly non-verbal. The results have been amazing.
In the post I referenced above, I mentioned the resource we've been using, Signing Time! kids videos by Rachel Coleman. She has a Deaf daughter (the inspiration for Signing Time!) and she also has a child with Spina Bifida and Cerebal Palsy who is able to communicate through sign language. Rachel ended up teaching all the kids in her neighborhood some sign language so her daughter could have some friends, as all the kids avoided her because she was Deaf.
It's a truly moving story and Rachel is hands down one of the most amazing people I've ever seen. The videos are extremely well produced; the songs aren't annoying like so many kids programs are. I can't say enough good things about them. Many PBS stations are now airing the videos and Rachel tours around and gives free performances.
The website for Signing Time! is at
http://www.signingtime.com, and they have a forum and chat room over there, too. Rachel also tours and does free signing events for the kids and families.