If twitter is blocked from your work or school, there are various ways to circumnavigate the problem. However, clever system administrators always stay ahead and try and play catchup to these workarounds.
The latest method I have found makes use of iGoogle and adding a widget called TwitterGadget. It even has integration for Gmail and works perfectly. As long as the TwitterGadget website is not blocked this method should work. If all else fails try out psiphon which is an Internet...