What should I be looking for in a baby mobile?

not an expert at all, but i'm thinking colorful, stimulating (the more interesting the better for development), not dangerous (especially if you live in an earthquake area!). maybe consider non-toxic or certain plastics/chemicals, especially if the baby will be touching it a lot, sucking on it, etc. (not just looking at it)

let us know if you find a cool shop!

Pottery Barn Kids have the cutest mobiles. Not sure about the price. Am guessing 30 or under? Or Babies R Us have a cute variety and it is cheaper but doesn't look cheap. That is where we bought our son's mobile of sailboats. Have fun shopping auntie! They both have websites to browse on line before going to stores or by online.