Windows only: Freeware system tray application Process Lasso monitors your running processes for CPU hogs and reins them in before they take over and freeze up your computer. Like previously mentioned Process Tamer, Process Lasso does this by lowering the priority of those processes on a runaway train to freeze-ville. Unlike Tamer, Process Lasso also offers a tonne of user customisation, so you can set default priorities by process or other rules for how Process Lasso deals with CPU hogs, like "Make firefox.exe run only on CPU #1 each time its launched."
In addition to the advanced process management and throttling, Process Lasso also handles advanced task manager duties. You can toggle auto-starting processes, kill processes, monitor CPU usage with a real-time graph, and more. Process Tamer (the similar app we posted in the past) handled throttling duties well, but Process Lasso offers an impressively superior range of features if you want or need more than Tamer offers. In all Lasso is taking about 10MB of RAM, so the footprint is reasonably small. Process Lasso is freeware, works with Windows 2000 through Vista.