Windows only: If you want a little extra eye-candy in your Windows management, T3Desk is an alt-tab alternative that gives you 3D windows arrangement and more.
Click on the image above for a closer look.
T3Desk works on all versions of Windows but it really shines in Vista and above where it can take advantage of Aero. After installing T3Desk you can use keyboard shortcuts to minimise and maximise windows to the edges of your monitor, arranging them in a pseudo-3D fashion. T3Desk can be tweaked in a variety of ways including how the windows are angled, animated, their level of transparency, the apparent distance from the viewer and how they transition from the virtual desktop back into use.
You can drag windows and dock them to the four sides of the monitor, use Aero Peek to see which windows are on the virtual desktop, and set an always include/exclude list for applications to easily exclude applications from the effects of T3Desk.
Some caveats about T3Desk: The biggest issue is that it won't work with multiple monitors. All 3D windows are pushed onto the primary monitor. Another minor issue is the inability to customise the application's hot keys. Those complaints aside, it works as promised and provides a novel way to arrange and view open applications.
T3Desk is free and Windows only. Have a favourite application for tweaking the appearance of Windows and managing your applications? Let's hear about it in the comments.