How do I check whether plugins are up-to-date?

I'm running Safari 5.1.2 under OS X 10.6.8. How do I check whether the installed plug-ins are up-to-date?

Yes, I know that the menu item Help > Installed Plug-ins lists all the plug-ins, but trying to track down one-by-one whether they are the current versions would be a tedious and time-frittering undertaking.