Windows/Mac/Unix (Firefox): The Aging Tabs Firefox extension keeps an eye on your open Firefox tabs, highlighting your active tab and fading the aging tags that you haven’t used in a while.

If you’re someone who’s perhaps a little too tab-happy in Firefox (a pack-rat for tabs, perhaps?), Aging tabs could be a great way to find the tabs that are ripe for the chopping block.

Aging Tabs [Mozilla]