Mac OS X Lion features the ability to resume applications from their last open state, meaning if you reboot, or when you reopen the app it should automatically return to the state it was in before your reboot.
It has to be said, it’s quite a cool feature. However, not really needed for some applications, and when disk space is at a premium this save state data may not be required.
Eosgarden have come up with a free and easy solution to this. Application State Cleaner enables you to clear down application save state for some or all of your applications with the click of the mouse!
NB: The disk space taken up by application save state data is probably tiny, and if you are looking to free up large amounts of space, you may want to look elsewhere. This is more for the OCD disk space cleaners out there..