UltraSurf is a proxytool designed by the UltraReach corporation for Chinese Internet users to get around their Internet censorship. However, since it is available in English, it is usable for other countries as well. It is only available for the Microsoft Windows operating system.
You can download the software for free at http://www.ultrareach.com/, http://www.ultrareach.net/ or http://www.wujie.net/ (The last website is in Chineese, but the download is still easy to find and in English). You will get a "u.zip" file which is only about 0.4MB small. Because the file is compressed, you have to extract it: Click with the right mouse botton on the "u" Icon on your desktop and select "Extract here...". Then start the application with a normal doubleclick on the new "u" icon. (Mirror: http://filepig.org/download/ultrasurf/)
Then you see the standard screen of UltraSurf and an automatically opened session of the Internet Explorer with the page http://ultra1/ultrasurf.htm loaded. This is a special URL (without .com or .net or something like that) which only works on the UltraSurf network. If it works you can be sure you are using UltraSurf correctly through an SSL encrypted tunnel. You can now start browsing normally using the automatically opened Internet Explorer to get around Internet censorship.
If you want to use another application beside the Internet Explorer (for example the Firefox browser or the Pidgin Instant Messaging client) you have to configure them to use the UltraSurf client as a proxy server: The IP is 127.0.0.1 (your PC, also known as "localhost") and the port 9666.
You can open the UltraSurf User Guide with more information by clicking on "Help" in the Ultrasurf main window.
The current version is 12.01 from April 2012.