You can unblock sites when you are at the school or at the office. To do this you have to bypass or disable the blocking software that is being used to block a web site. The easiest way is to bypass blocking software by using proxy server.
Proxy servers or anonymizers allow you to bypass web filters due to the way they operate. Proxy servers are special web sites outside your school's firewalls.
They could be easily accessed via the internet. These sites have their own IP address. Your web browser connects to a web proxy server and the proxy server makes connection with the blocked site. The proxy server then transmits you the contents of the blocked site. So you can browse the web site through the proxy site- even though it is blocked by your network firewall. This is achieved because it is not your computer accessing blocked web site but the proxy server.
Unfortunately, proxy sites got blocked fast. But you could always use the search engines to find new ones. Just enter something like 'school proxy', or 'myspace proxy'. You will find hundreds of links. Owners of the proxy web sites promote them to deliver new proxy web sites for you.
You've got to know it takes time for web site to appear on google search results. So it could be already blocked by the time you find it. To deliver new proxys fast web proxy owners use mailing lists. Just subscribe a list to find new proxy sites at your inbox every day.