Windows: If you need a little extra boost when you're working on your Windows machine, TopWinPrio offers on-the-fly adjustment of process priority based on which window is in focus.
TopWinPrio is a lightweight and free application that offers on-the-fly adjustment of Windows' processes. If you're uncompressing an archive, editing a photo and downloading something, TopWinPrio will give priority to whichever you have in focus. Start editing the photo, for example, and Photoshop will get the highest priority.
TopWinPrio is freeware, Windows only. Visit the link below to read more and download a copy.