I use window tiling with keyboard shortcuts a lot on my Ubuntu. However, back in the days when I was using an XP OS at work, I found a great tiling manager software called Splitview. The difference which Splitview creates is when you press -let's say- Ctrl+Alt+6 the window spans the right half of the screen. But, if you repeat the same key combination, this time, the window spans right 1/3 of the screen 
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So, I could practically tile 3 windows vertically which was obviously increasing my productivity. Since then (namely since Ubuntu 8.04) I am searching for such a feature time to time. Do you know of any similar extensions? To be honest, I don't want to try new X managers.