http://tor.eff.org/"Tor: An anonymous Internet communication system
Tor is a toolset for a wide range of organizations and people that want to improve their safety and security on the Internet. Using Tor can help you anonymize web browsing and publishing, instant messaging, IRC, SSH, and more. Tor also provides a platform on which software developers can build new applications with built-in anonymity, safety, and privacy features."
I've been using Tor for quite some time now - I even totally changed my computer set-up so that I could run a WinXP Tor server.
There isn't a site in the world that can detect who I really am or where I'm really coming from when using Tor (I've checked them all).
If you haven't played with this thing yet, you really ought to give it try. (It's free, of course). Pete