There are several times when websites may be blocked in your school, college or at work, though that is not the end of the world, and you would still be able to access the websites by using a proxy website which uses a different IP address than the one directly used by your computer.
This in turn helps bypass your administrator’s block on the actual websites like Twitter, Facebook, Orkut and so on.
Here is a list of proxy servers that you can use to access blocked websites in your school, college or at work.
Thanks for the proxy list Pavan. Do you use any other proxy servers to access blocked websites? Do let us know through your comments, so that users can use them as a alternative.