How to unblock websites at schoolFirst, why not look into alternatives to school, where you won't have stupid internet filters in the first place? But anyway, here's how you can unblock any website at school by making your own proxy.
Set up your own proxyThis is the most reliable way to bypass the firewall and unblock sites... but you have to do it yourself. Basically, you set up your own proxy on your home computer or on a web host somewhere, and use it yourself. Don't tell anyone about it, except maybe a close circle of friends. The more people who know about it, the more likely it will get blocked. But hey, if you can make one proxy, you can make more of them, so... :)
How to make your own proxy to bypass a firewallInstall Apache and PHP on a computer that has permanent access to the internet. Download and install a PHP script called PHProxy (you'll have to Google for it, its owner stopped developing it). You can also use CGIProxy, or Glype. Then, as long as you know your IP address, you can get to your proxy from anywhere. You can also set up DNS for it if you want, but that just makes it easier to block. So, if your IP is 123.456.78.9, you'll access your proxy by typing in http://123.456.78.9 at school.
psiphon turns a regular home computer into a personal, encrypted proxy server. psiphon is free and open source, and comes in Linux and Windows versions. It is easy to install, but if your computer is behind a home router it may require some configuration.
Peacefire Circumventor is similar to psiphon, but a bit harder to install.
Other ways to unblock sitesUse Google's cached version of the site. This will let you read just about any site, but you can't log in to member sites (like Myspace or Facebook). This may or may not also work with other search engines, like Yahoo and whatever else there is.
Translator sites can be used to access pages much like the search engine cache trick. Example: babel.altavista.com or translate.google.com
You can use RSS readers to access news sites instead of going to the site itself. www.bloglines.com is just one, but there are millions of these.
You can use "web accelerators" to unblock sites too. Like webaccelerator.google.com - UPDATE: This no longer works.
Unblocker/Bypassing ProgramsUltraSurf is free software and is available in English and Chinese. Once started, it opens an Internet Explorer type program that is automatically configured to allow you to browse websites through UltraSurf. Other browsers must be configured manually. The UltraSurf site itself might be blocked, so you may have to download this at home and bring it to school on a flash drive or something.
School firewalls block a lot of useful websitesSchool firewalls have been known to block a lot of educational and downright useful sites. In fact, the software they use to block things with is extremely ineffective at blocking access to anything (as this article has just proven). That also isn't even taking into account the fact that there are a lot of interesting videos on YouTube that even teachers might consider educational, and that there's a lot to be learned by interacting with people online on social sites. For more information about internet censorship, go to Peacefire.org.
Researchers have found that commercial filtering technologies mistakenly block access to content related to women’s health, gay and lesbian rights groups, and sexual education for teenagers. Everyone's Guide to By-Passing Internet Censorship for Citizens Worldwide