Psiphon is a new open source project from the University of Toronto that aims to give people unfettered access to censored web sites, particularly those blocked by oppressive governments. Basically it works by allowing people with uncensored internet access to act as proxies for those without. Unlike with Tor, the "psiphonite" (i.e. the person in the censored country--memo to U of T: this awful terminology is likely to scare away novices) doesn't need to install any software--they just connect to the psiphonode's unique address. Psiphon isn't based on a central server, and psiphonodes' addresses are distributed organically, i.e. by word of mouth. This means Psiphon isn't anonymous like Tor, but it is secure and encrypted. Currently the psiphonode server software is available for Windows and Linux, with Mac support promised soon. For more information check out the Psiphon FAQ.

[Thanks, Ramesh!]