Are you ever doing something where you want the window on top, even when you're looking at another window? I talk on AIM with friends of mine sometimes while playing solitaire, and I like to have the AIM window visible all the time. This utility will let you do that. It sits in the system tray, and if you left-click on it, it will make the last active window always on top. Other windows can still have the focus, but this window will still be in front of those. If you middle-click on the tray icon, the last window will no longer be always on top. Right-clicking will bring up a menu describing your choices, and allowing you to quit. Unfortunately there is a bug in the menu code; if you open the right-click menu and then click elsewhere, the menu doesn't close. You must choose one of the options there to close it.
Application (32-Bit Windows)
Source (Visual Basic 6)
Support classes for source code