This web site doesn't have many links to random off-site stuff, because for one thing, it's not 1996 anymore. But, we did baby-oriented American Sign Language with our daughter and had such a great experience I wanted to make this recommendation.
Doing the baby-sign thing is awesome, and specifically, we really, really, really love the DVDs from Signing Time.
They're very creatively made, with decent production values, and the music is good (as kid's music goes -- it'll definitely be stuck in your head more than you want), and since sign is a four-dimensional language, it's much easier to learn than from books. And, unlike Baby Einstein pablum, with its vague hints of intelligence-boosting, they actually are very educational, both for parents and kids.
Specifically, I recommend the Baby Signing Time set, which is $50, but easily the best $50 we ever spent on baby paraphernalia. The first few volumes of Signing Time proper (i.e., post-Baby) are a bit disappointing -- they were made early on, and, while I don't want to say anything really bad, they're just not up to the quality of Volume 4 and later. They do cover some really useful signs, but many of those are also covered on the Baby discs.
Anyway, highly recommended.