Highlight updated tabs
Highlight tabs whose titles have changed (for example GMail updates the inbox unread count upon receiving new mail) in the same way as unread tabs.
It might be even more useful if it could be triggered if anything on the page changes.
I agree with Lythande that this should (optionally) be available for individual tabs. You don't want every single tab highlighted.
This could come in handy (sorry, keeping my lousy 8 votes in case I think of more 'suggestions' ;) but I'd prefer an option added to individual tabs to "highlight this tab on changes".