Windows only: If you've been holding out for the official release of Windows 7 but want to get your hands on that superbar, ViGlance is the one-step answer.
Once installed and running, your taskbar instantly changes form, grouping windows into single, 48x48 icon sections. Hovering over each icon shows a popup telling you the name of each window or the names of the windows in that group. Each group popup is dynamically resized via "glide" animation—based somewhat on the Aero Peek feature in Windows 7—to fit to the size of the text to be shown, making movement across the task bar seamless. And while it doesn't boast every feature of the superbar, it is a nice tweak if you'd like to bring similar taskbar functionality to your pre-7 Windows installations. ViGlance is freeware, currently supports Windows XP, Vista and Windows 7.