FoxyProxy

FoxyProxy is a free, open-source advanced proxy management tool that completely replaces Firefox's limited proxying capabilities.FoxyProxy automatically switches an internet connection across one or more proxy servers based on URL patterns. Put simply, FoxyProxy automates the manual process of editing Firefox's Connection Settings dialog. Proxy server switching occurs based on the loading URL and the switching rules you define. Animated icons show you when a proxy is in use. Advanced logging shows you which proxies were used and when. QuickAdd makes it a snap to create new URL patterns on-the-fly. FoxyProxy is fully compatible with Portable Firefox, has better support for PAC files than Firefox itself, and is translated into more than 25 languages.

• Want fine-grained control over which websites load through proxies?
• Live in Belarus, Burma, China, Cuba, Egypt, Iran, North Korea, Saudi Arabia, Syria, Thailand, Tunisia, Turkmenistan Uzbekistan, Vietnam, or one of the other nations who censor the internet?
• Can't get to MySpace from school?
• Can't get to GMail at work?

Then foxyproxy is for you!

FoxyProxy does not inherently make you anonymous

Please read this important note if you require thorough privacy and anonymity.

Some FoxyProxy Features

• Animated statusbar/toolbar icons show you when a proxy is in use
• Define multiple proxies
• Define which proxy to use (or none!) for arbitrary URLs using wildcards, regular expressions, whitelists, blacklists, and other conveniences
• No more wondering whether a URL loaded through a proxy or not: FoxyProxy optionally logs all URLs, including which proxy was used (if any), which pattern was matched, timestamps, etc.
• Out-of-the-box support for Tor with the unique Tor Wizard - zero configuration!
• Temporarily or permanently dedicate all URLs to go through a particular proxy
• Temporarily or permanently disable use of a proxy
• Automatically add blocked sites to a proxy and have them reload through the proxy
• Optional status bar information about which proxy is currently in use
• Complete Proxy Auto-Config (PAC) support
• Download a link using one of your defined proxies with a simple right-click (coming soon)
• Unobtrusive presence, stable execution, premier support
• Optionally force Firefox to perform DNS lookups through a SOCKS4a/5 server. Note that Firefox without FoxyProxy always performs DNS lookups through a SOCKS5 server if you've defined one. Only with FoxyProxy can you instruct Firefox to not use defined SOCKS5 servers for DNS lookups.

Source: FoxyProxy
Download: Extension