Windows only: Like Caffeine for the Mac, tiny Windows app Insomnia will keep your computer awake for those long-running jobs that need its full attention.
Whether you're downloading, converting, burning, streaming or performing some other task that requires your computer to be awake, sometimes the program in question doesn't do it on its own. For those situations, this small app will keep your computer running for as long as its small window is open. The only quirk is that Insomnia insists on staying on top of all other windows, which can be kind of annoying. At the same time, though, that "feature" does help you remember when it's running, so you don't forget to let your computer sleep when it can — no need in draining excessive power for no reason.
Insomnia is a free download for Windows only.