Those Felix Ungers among you who want more control over the details in your life will get a kick out of FreeSnap (free). This memory resident app--available in 32-bit and 64-bit versions--controls and resizes windows using keyboard shortcuts, letting you "snap" the window to any corner or screen edge.
The shortcuts to snap windows around with FreeSnap all use the Windows key, so you'll have to have a keyboard made in the last 15 years to use it, and you'll have to be careful of other apps that also use that key. (Also, be careful with Win+? to bring up the help menu. If you're not holding down Shift and hit Win+/, you'll close the current window--which means that if you're at the desktop, you'll launch the Windows shutdown menu.)
One drawback is that if you have your window at a certain non-standard size, and use FreeSnap to snap it into a predefined quarter or half of the screen, you can't undo. You can fine-tune the size of the window using another keyboard shortcut, though.
FreeSnap uses only a few megabytes of RAM while in memory and almost no CPU, and can easily be shut off from the Start menu if you need to do so (though there's no tray icon). Since there's no tray icon, it's be easy to forget about it while it takes up space in your RAM. Even though we all have way too many tray icons, it would have been nice to have the option.
For those who want an easy, keyboard-based way to manage many windows for free, though, FreeSnap is the app for you.