You probably already know that you can do Win+<Left/right arrow> to maximize to half of the screen, Win+<Up/down arrow> to maximize/unmaximize, and Win+Shift+<Left/right arrow> to send to other screens, right? That's already a lot of the functionality promised by a lot of OS X tilers (Though Slate clearly has quite a bit more, too). Divvy is also available for Windows (http://mizage.com/windivvy/), and if you look around there are quite a few other options for "Windows tiling window manager," some of which are a little more "genuine" in that they force the tiling. You can also get alternative shells that provide tiling.
