The Raspberry Pi is the most well known single board computer (computer that fits in your hand). It is used by makers and hobbyists for their projects but also by companies as the 'brains' in their computerised products. It's low cost (about $35) makes it attractive for educational purposes which is the original goal behind this computer.
Unfortunately we can only recommend this device as a player for static content. It is not powerful enough to play video and animations reliably. Our Linux How to describes a few tips specificaly for the Raspberry Pi.