Web proxies are very slow, I usually use proxies from
FREE SOCKS 5 PROXY, SOCKS LIST FREE . FAST NEW FRESH FREE PUBLIC SOCKS 5 PROXY
Click "check" to see if the proxies are working, and use the proxies with the lowest response time. I don't use proxies with a response time of more than 7K ms as they're too damn slow for my needs.
When you find a good proxy and are using Firefox - Go to Tools>Options>Advanced>Network and click "Settings..." under Connection then select "Manual Proxy Configuration" and enter the proxy IP next to "SOCKS Host:" and the Port next to "Port:"
The IP and Port are shown like XX.XXX.XX.XXX:XXXX, the IP is the first set of numbers and the port, separated by :, is the second set of numbers. If you want to go back to your original connection just check "Direct connection to the Internet" where you entered the proxy info.
For IE6 - Go to Tools>Internet Options>Connections>LAN Settings and check "Use a proxy server for your LAN (blah dial-up VPN turkey twat)" then click on "Advanced" and enter the proxy and port next to "Socks:" and click OK. Deselect "Use a proxy server for your LAN (blah dial-up VPN turkey twat)" to go back to your original connection.
I think that covers it all but I'm a little bit stoned so I dunno. I have never used IE7 but it should be about the same for that.