The Tux Droid Robot is a great gadget gift for Linux fans available on Think Geek.

The Tux Droid Robot has similar features as the Nabatztag rabbit, but comes in the shape of the Linux Penguin mascot. Tux is wireless and connects via a USB device that comes in the form of a fish that plugs into a USB port on a Linux machine.
With the included software you can have the Tux Droid monitor any number of different events and have him react with different lights, sounds, and movements to let you know what's going on. From dancing for e-mail alerts, acting as a remote control for your PC and even doubling as a wireless VOIP phone Tux does your bidding.

The best thing is that you can hack and customize the open source software with Phyton widgets. A plethora of interesting inputs and outputs are available for your programmatic pleasure. Tux can blink his eyes, light-up his eyes, swivel on his base, flap his wings, talk. Tux can also hear, tell how dark it is, sense a push on his head, a push on either wing and accept commands from the included IR remote.
Measurements of Tux are 210mm x 180mm x 140mm and it runs on Atmel AVR RISC microcontrollers.

Think Geek sells this great Linux USB toy for $99.99.