We have an infant stim mobile that my five-month-old LOVES. It doesn't rotate or play music so we attached the hanging part to another mobile that does both. Now he watches black and white cards rotate slowly to the tune of "Twinkle, Twinkle, Little Star" and seems to like it long enough that I can wash my hands after a diaper change.
This is the one we have--if you're crafty you could probably make your own for a lot less. http://www.amazon.com/gp/product/B00009ZIKH

This is the one we have--if you're crafty you could probably make your own for a lot less. http://www.amazon.com/gp/product/B00009ZIKH