I see ads for this all the time: baby sign language. As a deaf woman, even though I can read lips and speak just fine, sign language is something we've been encouraging with baby since day one. Babies are capable of signing their wants and needs long before they are able to speak them, so it's certainly a worthwhile pursuit. That said, I cannot fathom why anyone would pay for books, DVDs, or software to do this.
There is no difference between baby signs and adult signs. So if you know adult signs, you're all set already. If you don't, unless you plan on using ASL as the primary language in the house long term, you're only ever going to need a handful of signs. It's about keywords like, "drink," or "bed," not full sentences. If all you need is to learn a few words, there are numerous resources available to do this for free!
The Deaf community is all about inclusion, whether you're hearing or not. You'll be amazed how many free resources are out there for those who take the time to look. Depending on where you live, you may even find ASL workshops available nearby. Unless you're taking an actual language course at a college, for language credit, there is seldom any need to invest a bunch of money.