KillMe

the author of this app says:

AutoClose continually scans your computer at the user-defined time interval and closes any open programs that exceed a user-defined threshold. This is a great timesaver if you're tired of constantly having to monitor the state of your computer. Programs are closed in reverse usage order, so the least used programs are closed first, leaving those you're currently using open and more responsive because they'll have more memory to work with!

Requirements

2.0 and Above