Hi Hypatia,
I know exactly what you mean. Have you looked at bilby.net they have alot of resourses although not free.
but I use a website that was found by Mtb999 and it is a free resource for AUSLAN The best site is:
http://www.auslan.org.au/ - can look up signs for words and watch a video on line as to how to do the sign
If you go with ASL it might be easier to get resources for yourself and if you are not going to be speaking with deaf people then there is no problem. It all about being able to communicate with your child and you want to make that as easy on you and bubs as possible.