If you’re running lucid, you should have the latest version 3.6 of Firefox from Mozilla.
Here are some hidden features disabled by default, similar to Compiz expo and shift-switcher.
Open a new tab and type “about:config” into the address bar. Then find the following value and set it to true instead of false:
Once activated, you can preview tabs using keyboard shortcut Ctrl + Tab (or Ctrl + Shift + Tab if you want to have the search engine as well).
To activate the display, also change the following option to true: