AeroSnap is a small application developed by Christian S, that adds Windows 7's aero snap-to functionality, to Windows Vista.

After its installation, you can drag any window to the top of your screen to maximise it, take it to the left or right to snap it to the side and re-size by 50 per cent.
<object width="425" height="349"><param name="movie" value=" 0x0&hl=de&fs=1"></param><param name="allowFullScreen" value="true"></param><embed src=" 0x0&hl=de&fs=1" type="application/x-shockwave-flash" allowfullscreen="true" width="425" height="349"></embed></object>
When you drag it back to the last position, the last window size will be restored.

To run AeroSnap on your computer, you need Windows XP or Windows Vista. You need also .Net Framework 2.0 or higher. It also works with multiple monitors!