Firefox tip: App Tabs

Via Luke: Say cool cats and kittens, do you always open the same few 'sites when start your web browser?  And keep them open?  Gmail, for instance, or Pandora?  Then this groovy new feature is for you!  When you open the site, right click the tab and select "Pin as App Tab".  Whenever you start FF4, this tab will automatically open and remain open as a thin tab on the left (so it doesn't take up too much space).