Well, Silicon Railway has announced their Arduino clone, which is called the LEDuino. In its basic form it is totally compatible but has a smaller USB port connector, and has a power switch. However, it can also be configured with a DCC interface for railroad buffs, a I2C interface, and/or a CAN interface. Its a well-connected board.
You can read more about it here, or go to their website, or even buy one on EBay. The Arduino original site is here.