Moving a window without bringing it to the forefront!
I actually saw this tip on Tekzilla, but it is so cool that I had to post about it. What it lets you do is move windows that are not the currently active windows without bringing them to the forefront. It is hard to explain, but you'll get a good idea once you try it. You just have to hold down "Command" and click on a window that is not currently active to move it. It doesn't work with all windows, but it usually works well. Thanks for the tip Tekzilla.