http://community.babycenter.com/post/a5559325/free_story_time_with_beebo_the_baby_signs…
Check out this link, its about the benefits of using sign language with babies.
We used it with both our little ones, and it demonstrates your babies ability to communicate with you well before they are physically capable of speaking. Our 4 year old still used the signs even when she was talking, she would speak the words and do the signs as well. Now she helps teach her 18month old brother the signs.