Launchy www.launchy.net (Windows)
Launchy launches (duh) applications, fi les, folders, or searches via a command-line–esque interface.
ObjectDock www.stardock.com (Windows)
Organize your application shortcuts in a toolbar that mimics the look and feel of the Macintosh dock, complete with icon animations. It will even mimic Windows Taskbar buttons. Add in extras (docklets) like real-time clock and weather forecasts, even a fully functional Windows Start button and Recycle Bin, to get everything you need.
QuickSilver www.blacktree.com (MacOS)
This open-source launcher takes plug-ins that allow it to do almost anything you want in the MacOS.