So obviously, TOR needs a large amount of servers and as TOR network is not a commercial organisation, it requires voluntary supporters. You can be one of them and turn your Raspberry in a TOR relay.
Step 1: Parts needed
- Raspberry Pi
- power supply
- network cable/connection to the Internet
- SDcard with Raspbian (you can find all necessary installation intructions here: http://www.raspbian.org/RaspbianInstaller)