There are three kinds of Tor relays: exit relays, middle relays and relay bridges.

Middle relays are servers which are openly part of the Tor network. All incoming and outgoing traffic that passes through these relays is encrypted and anonymous, so they're quite safe to run on your home or office PC.

Relay bridges are just standard middle relays that don't advertise as such, which makes them more difficult to shut down. They're actually pretty safe to run on your home computer, but you run the risk of being placed under surveillance by governments and other watchdog organizations working to sniff out Tor relays.

Exit relays are the last stop when your browsing request leaves the Tor network, and it's their IP address that's revealed if anyone tries to monitor your Internet activity. That means that running an exit relay on your personal computer is risky, since anyone could use the Tor network for unscrupulous purposes and it would look like they were doing so from your home computer.

For the purposes of this article we'll be focusing on setting up a middle relay, since the other two are potentially dangerous to operate. To get started, the stable Vidalia software bundle from the Tor Project website and install it.