We work ASL into our vocabulary when speaking with our son.  I learned a few signs from the ASL Browser; more, food, drink.  We started using those when he began to eat solids.  In January I discovered our local library has a collection of Signing Time videos.  Our son enjoys watching the videos.  His favorites are Leah’s Farm and Zoo Train; the ones with animals.  A new sign language video dictionary, Signing Savvy, came online in January.  It has a larger sign collection and videos which can be played in slow motion.  You can pay for access to larger videos and more features but the free & registered access is sufficient for us.