If you work on Mac OS X, and despair at the lack of ways to keep certain windows "afloat", or "always on top" (if you’re familiar with Windows applications that do similar things), then Afloat is the utility for you! Did I mention that it’s free?
Upon install, it adds itself to the common Window menu of every application, giving you a bevy of options to control the window of the app you’re working with.
It allows you to keep one or more windows floating/pinned above others, or turn them translucent, allowing them to be visible and let clicks "fall through" to the windows behind it.
For example, I’m on a lot of conference calls, and need to take notes, but also have other windows open doing research about the subject matter, etc.
I had been using (and LOVE) a free utility called Shift It to emulate Windows 7’s "Aero Snap", i.e. the ability to snap a window to the right half of the screen, or left, or top/bottom/etc. This works wonderfully, although it is a key combination, versus a drag/drop operation.
I was using a different application called Cinch, which I actually paid for, but there are some minor bugs that are being worked out before I can use it on a day to day basis. It also behaves weird with VMWare Fusion, not always snapping properly, but I’m sure that it will be updated soon enough.
So, if you’re a fellow window-holic like me, grab a couple of these free utilities and start making the most of that [growing but] limited desktop space!