Go get "Always On Top" (which coincidentally is the title of this thread): http://www.labnol.org/software/tutor...s-on-top/5213/
There is a download link and instructions. Pretty simple, and I just tested it on my Win7 machine. Basically just install it (takes 2 seconds), then press CTRL+Space and the active window will stay on top. Press CTRL+Space again and it'll revert back to acting normally. Works pretty good.
EDIT: I did discover you can do this on multiple windows. I had a browser window "pinned" and skype also "pinned" and both would stay on top of all other windows (but I could put skype on top of the browser and vice versa). There is no way to identify a pinned window, unfortunately, but if you try to move a window on top of it, it becomes obvious.