[psykotic]

Or you can select the window with alt-tab, press alt-space to open the window menu, press 'm' to select 'move' and then use the arrow keys.

I use this all the time when windows go completely off screen and you can't grab them with the mouse. That can happen in all sorts of surprising ways.

[drv]

And once you've moved it with an arrow key, you can then move it freely with the mouse until clicking.