OKAY short of telepathy this is the best way to talk to babies. We taught my younger brother sign language when he was a baby. We still use some of the signs, usually water and potty, especially in public.
braille alphabet | braille-alphabet.gif...to use with Knots on a Counting Rope
Auslan sign alphabet chart - been looking for this for ages
British Sign Language Finger Spelling Alphabet
Kids with aphasia and/or CP sometimes can learn/demonstrate the spelling of words through signing the letters physically rather than spelling aloud.