Remember window sizes and placement when unplugging and replugging second monitor

Here’s something that sucks: 1. Plug in external monitor to laptop (Mac OS X Leopard in my case). 2. Arrange your windows to have the IDE on one screen and browser on another. (Etc etc. Resize, rearrange, fuss, fuss, fuss.) 3. Unplug monitor to run to a meeting, or whatever. 4. Goto 1. I’d like to replace step 2 with “computer remembers exactly how I had it and just puts it back that way”. (I personally only need a solution for Mac but collecting solutions for other systems here might be useful to others. I’m sure it’s a common problem.)