I originally published this a few years ago. I'm bringing it back up because I was recently asked about this issue again.
I can't tell you how many times I've presented a website or tool at a workshop and a teacher has said, "that's great, but my school blocks everything." Having useful sites blocked is frustrating for everyone. I've been there. In the fall of 2009 I returned to school after the summer break to find that all of the sites (VoiceThread, Wikispaces, Blogger, Animoto, and others) that I had planned to use were blocked by the new filter that had been in place. Fortunately, my principal was willing to listen to me and some of my colleagues and he overruled the network administrator. If you find yourself in a similar situation, try these things before throwing up your hands in frustration.
Tactics for getting access to the websites that you want to use.
1. Attitude: don't sit back and complain quietly, don't sit back and complain loudly. Rather you should go to the top with research and a plan. Straight Talk from the DOE is a good place to start that research.
2. Relationships: if I didn't have a good working relationship with my principal I wouldn't be able to walk into his and have him seriously consider what I ask for.
3. Persistence: changing a school's or a district's policy isn't going to happen overnight.
4. Recruit supporters: if it's just you leading the fight you might be looked at as "that crazy teacher," if there is two of you you might be looked at as "those crazy teachers," but if you can get a third supporter then you've started a grassroots movement. This is an idea that I borrowed from this Ted Talk by Derek Sivers and from Arlo Guthrie's Alice's Restaurant.
Update: Shortly after this post went live Doug Johnson emailed me with a link to something he wrote on the same topic a couple of years ago. Doug outlines ten steps in his post. But what I like best about his post is the chart that he uses to show the correlation between "knowledge of educational uses" and "permissiveness of internet use." Take a look at Doug's chart here.