Windows: Most laptops have power management profiles set up to conserve energy when off the charger. But if you need that extra kick on certain apps, Full Throttle can help you out.
The app sits in your system tray, and you can manually add applications to its watch list. When you run those programs, Full Throttle will switch your PC's power management settings to a high-performance mode until you're done with it. Once you close the app, it automatically switches back to power-saving mode.