"Arduino is a single-board microcontroller designed to make the process of using electronics in multidisciplinary projects more accessible." -wiki
With a $25 Arduino board you can program DIY projects on the cheap.
Were talking, DIY Drones, Games, Robots, Toys, Hacks, Tools, and much more.
Dream up all kinds of crazy projects with this board and make them come to life easy, Arduino boards have an array of different functions, there are alot of snap on and solder on packages you can get for these boards for other purposes like bluetooth chipsets, wifi chipsets, and video chipsets for the homebrew game-age!
So if your a DIYer, I definitely suggest this board.