Chameleon is a little application that allows you to make windows of your choice transparent.
Some might point out this could be useful to partially hide the video you're watching while at work, and while that's true, it's also a useful way to multitask. You can write in a transparent Word window, while reading an internet page in the background, for example.
After installation, Chameleon opens with a list of open programs. Click any and you can set their transparency. You can also add programs to the Hide Group. Window in this box will disappear when CTRL + Win are clicked together. That feature really is designed for people trying to avoid being caught time wasting on their PCs! Alternatively, you might use it as a way to keep you desktop uncluttered while having lots of programs open.
Chameleon itself minimizes to the system tray, so doesn't get in the way, and it also remembers your settings from the previous session, so you don't need to organize your applications every time you open it.
As a tool to hide and give transparency to windows, Chameleon is pretty neat.