Using Firefox 0.9 on Windows XP or on Mac? Go to Help — Keyboard Shortcuts and (among other things) you can move between tabs with the keyboard. There are heaps of other keyboard shortcuts there too.
Control Shift Tab
Folks, I'm sorry, but the comment spammers send about a million more comments than real readers do and I can't stand the spam. I've disabled comments again. Feel free to respond to @miraz on Twitter or to email me through the contact form on the site.