Recommendations for Windows 7 feature to split windows in half on Mac?

I'm looking for some free software that allows you to drag a window (most of the time it would be Chrome) to one side of the window, and it will automatically fill up half the screen, and then do the same for another window to fill up the other half of the screen.

If you're unsure what I'm talking about, see this (skip to about a minute):

http://www.youtube.com/watch?v=JHGg_A4gebQ

I use this feature occasionally, and would like to be able to just move windows to the side like this, instead of having to position each window individually and manually resize it.

I know stardock (I think) have this feature, but you have to purchase it.

Anyone know of any free alternatives out there?

Thanks.