Notch up another useful pet project for the Raspberry Pi. Adafruit offers a tutorial for combining the Raspberry Pi and Tor, which routes traffic through a worldwide network to preserve anonymity. They christened it the Onion Pi, since Tor originailly stood for The Onion Router.
The project creates a wireless hotspot from any old Ethernet connection and automatically routes it through the Tor proxy. The little project is designed to put smartphones, game consoles, and other systems onto the Tor network that wouldn't normally be easy to route through a proxy, but it could also serve as a decent introduction to working with the Raspberry Pi and networking technology.
Assembling the entire thing is inexpensive--if you already have the Raspberry Pi and an Ethernet cable, all you'll have to shell out for is a USB Wi-Fi adapter and a 4GB SD card to hold Raspbian. Adafruit also sells an entire kit for $95, but if you don't care about a case for the Raspberry Pi, you can probably throw together the required parts for less than $50.
Getting the Onion Pi up and running is as simple as following Adafruit's instructions. Installing Tor requires a little command line work, but the directions are straightforward and easy to follow. With the wireless set up, you'll be one step closer to Internet anonymity--and so will anyone who comes to visit your house and uses your Wi-Fi network, since the access point itself routes data through the proxy.