In Windows 7, it's possible to do various resize operations by dragging windows: drag window to top of screen, and it'll be enlarged to fill whole screen. Drag it to left edge and it'll cover left side (50%), same for right edge. Also, bonus points: resizing window to top of screen keeps width but changes height to cover screen from top to bottom. In my opinion, that's way better than keyboard shortcuts.
Is there a way (with or without installing 3rd party software, preferably free) to do this in Mac OS X (10.6)?
Related, but not same: What keyboard shortcuts move, resize, and maximize windows under Mac OS X? I also checked out programs in answers, but all of those are for keyboard shortcuts.