Is your boss clamping down on the hours you spend playing Farmville on Facebook? Are you blocked at work from accessing 4chan and your other favorite websites? You can use something like Try2StopMe, one of probably thousands of website proxy services that allow you to access your favorite destinations through a middleman. Don’t expect this service to remain accessible long: like most proxy services the various content filtering subscriptions used by corporate firewalls find and block these things pretty quickly. Plus, you have no assurance that the middleman isn’t keeping a copy of everything you send — like your Facebook login credentials — for its own nefarious use later.
Try2StopMe is powered by Glype, which looks to me like a newer version of the old CGIProxy perl script I used to run ages ago. Best of luck if you find yourself in a position to need something like this.