There are a large (and ever growing number) of Add-on boards for the Raspberry Pi that be be bought now. Most come in kit form and need soldering up- some can be purchased soldered up for an additional cost and a few come fully assembled.
The current list of boards that I support is
|Gordon’s LadderBoard||Nunchuck via Multichuck
MotorPiTx PiRingo MiCroCon AdaFruitMatrix PiMatrix PiDie