Until now, it was difficult to completely anonymise your browsing and filesharing habits. VPN services were available for a small fee each month, but most people rely on the sheer volume of filesharing traffic to keep themselves relatively anonymous in the swarm.
Of course, that's not terribly effective, so filesharers have been crying out for an alternative, but free, system to protect themselves from the prying eyes of Anti-P2P companies. Enter BitBlinder.
BitBlinder is a free, cross-platform (doesn't have Mac support yet, though) Bittorrent client and internet browser. It claims to offer completely anonymous Bittorrent transfers, as well as hiding your IP address while browsing the web, and bypassing some web filters.
It achieves that by a sophisticated P2P network of its own. Instead of your computer connecting directly to the host, all the traffic is passed through other users of BitBlinder. The data is encrypted and goes through multiple peers before reaching you.
Each peer only sees the IP address of the peer before it, and the host of the file only sees the peer at the end of the list. How can it be offered for free? Because for every chunk of data you download, you have to ferry someone else's. A ratio system is in place.
Users start with 2GB of credit, and earn more by just leaving the program running. Obviously that'll use up plenty of your bandwidth, so if you're on an ISP that operates a "fair usage policy" then be careful of how much you leave it on.
If you don't want to be bound by the rules, then there'll be an option to buy credits that'll give you a chunk of ratio without having to share it. That could be an option for those limited by their ISP.
Of course, as your transfers will be passing through several computers before reaching you, speeds are impacted slightly. However, the overall impact is low compared to the impact of a poorly seeded torrent on your speeds. If you're getting slow speeds, then it's likely that something else is the culprit.
The BitBlinder client is a modified variant of BitTornado, and the browser it comes with is based on Firefox. At the time of writing, it's invite-only, and the team behind it are limiting signups due to demand. You can go and put your email address in on their website, and they'll let you know when more become available.