The Raspberry Pi had a birthday over the weekend. It's a fantastic tiny computer project that's come a long way in only five years. I'm applying to a number of conferences right now and hope to give a presentation on how I've used them in conjunction with MIDI gear to make some clever things!
There are tons of kits you can buy on Amazon. I strongly recommend sticking to the RaspberryPi 3 if you can. It's a night-and-day difference from 2.
Although I feel bad saying this on the Raspberry Pi's birthday... You should also check-out the C.H.I.P. computer if you're into tiny, hackable computers. I love it and actually prefer it to the RaspberryPi for a number of reasons.