Windows: If you have a lot of windows open, it can be helpful to see an overview of them all at once. Mission Control / Expose Clone W7 brings OS X Lion's Mission Control feature to Windows.
There are a lot of Exposé clones out there for Windows, but if you like Lion's new Mission Control -- where it groups similar windows to save space -- Mission Control / Expose Clone W7 is a good alternative. Not only does it group similar windows, but it has a lot of shortcuts built-in, like previewing thumbnails with a right-click and minimising all but one window with Ctrl+Enter.
It isn't perfect, unfortunately -- to keep it running in the background, you need to launch it from the command line with the
—resident flag, and it doesn't really work well with multiple monitors. Also, we'd love the keyboard shortcuts to be customisable. Still, it's currently in beta, so hopefully it'll improve more as it goes through testing. Hit the link to check it out, and be sure to read the readme for more info on how to install it and use all its keyboard shortcuts.