This is something everyone wants to do right. In most of the offices personal email, social networking sites, chat clients and alternative browsers, are all banned. Here is a nice little trick to access gmail and post tweets, right from your office firewall.
1. Just go to Pageflakes, a nice web application which I covered a year back.
2. Create a new account and browse for the email, twitter and facebook flakes from the flakes gallery.
Note: "Pop Download" must be enabled in your GMail settings, so configure this from your home before you try this at your workplace
3. Now go to your pageflakes home page and configure your new flakes and be surprised!