I'm trying to find a arduino board that can be programmed to play vocal music through a speaker and have a USB port to hook up your smartphone and play music through it. Is that possible? Forgive me for my lack of education with arduino. 
P.S. Can a arduino board be programmed to move gears as well?
the arduino is not really great for media, let alone streaming media, keep in mind its an 8 bit cpu with limited amounts of ram, the due may suffice though its not quite polished yet
yes an arduino can move motors and gears with appropriate hardware drivers to deal with the load, which is a common factor in any microcontroller system, you have brains and brawn, its rare to see both in the same package, much like in real life
as far as your question in the title, there are a uncountable amount of arduino's, clones, workalikes, and compatibles in many different form factors. the world is wide open there, or you could make your own as well. (its kind of like a PC in that regard, its just a bunch of easily available parts in a standard configuration)