Today I've successfully made a command that with a push of a button
simulates the Win+Left (or Right) on windows.
Just to clarify, we are talking about Gnome->Metacity.

Essentially it moves the window to the side you choose
and makes it as big as half the screen, very convenient for working on 2 things together.

In just a couple of steps you can have it too!

1. run gconf-editor, go to the path /apps/metacity/keybinding_commands/

now this is the commands you can edit and create for yourself, however for some reason it doesn't allow you
to do multiple commands in 1 so I had to create a shell script that it would run, no biggy

2. open your favorite text editor, write inside

#!/bin/bash
wmctrl -r :ACTIVE: -e 0,1,1,640,-1 | wmctrl -r :ACTIVE: -b add,maximized_vert

And call the file "left" (or whatever) and save it in your home directory (or whatever)..

Next make another file:

#!/bin/bash
wmctrl -r :ACTIVE: -e 0,640,1,640,-1 | wmctrl -r :ACTIVE: -b add,maximized_vert

And call it "right" (or whatever....)
Now we have 2 files that do the commands we want.

back to the first step, we still have the windows open (I hope you do)..
so, in the gconf-editor path /apps/metacity/keybinding_commands/ we choose 2 unused commands (blank)
and write down ~/left and on another command ~/right (the paths to the files we created)...
Let's say we used command 1 and command 2 (for left and right accordingly)

Now we'll go to /apps/metacity/global_keybindings and in the command 1 value we'll write "<Super>Left"
and on the command 2 value we'll write "<Super>Right" (or whatever you want).

That's it! you now have a function that can resize your window
to the left or right half of the screen.

Enjoy!