The World's Gate, Inc, released GProxy in Nov 2007.
GProxy is a Firefox/Thunderbird add-on (tool bar and status bar icon) that helps users to manage and switch proxy settings easily. It supports GPass, FreeGate, UltraSurf, Garden, and other proxy systems, with Chinese, English, and Farsi interface.
Many users consider Firefox a more secure and convenient browser. However, when used it with FreeGate, UltraSurf, or Garden, they had to change its proxy setting manually, and reverse the setting after use. GProxy aims to solve this problem.
GProxy is available for download as a freeware for personal. To install it in Firefox, just drag-drop the download file to the Firefox window. To install it in Thunderbird, use the Tools > Add-on menu.
I Don't Take Credit for Creating this Add-on, all credit goes to the Gproxy Team
I edit the Add-on cause i can't use it with my Firefox 4.0.* so i got inspired to check inside the Box called "install.rdf" and edit some stuff, thou am not a developer, but i wish to let other who find this useful to enjoy it as i do.
Firefox and Thunderbird is the application that well verified to work well this Add-on.
Have a nice time using it