App to keep windows within the display

[entitude]

I'm working on a macbook pro with snow leopard, and I was curious as to whether there was an app or feature that would keep all my windows within the confines of the screen. I don't want to maximize my window to the edges of the screen, I want to be restricted from dragging windows so that their edges go off the screen, even if they aren't maximized. (I'm using RightZoom for that.) This is my first mac, and while I'm quite computer-literate I don't remember ever seeing something like this, for any operating system. Any ideas? (If I've posted in the wrong forum or missed a thread addressing this, let me know. I'm new to the site.)