If you like the look of Windows 7's great new keyboard shortcuts but aren't planning to upgrade for a while, Windows 7 Shortcuts enables some of the best Win7 shortcuts for XP and Vista.Download here.
Win+Left/Right arrows: Dock the window to each side of the monitor
Win+Up arrow: Maximize the active window
Win+Down arrow: Minimize the window/Restore the window if it's maximized
Win+Space: All windows are made transparent so you can see the desktop
Win+Home: Minimize all windows but the current window
Arranging windows in XP sucks, as I have lamented before. These keyboard shortcuts are really useful, and I can't wait for Windows 7 to be released so they are standard issue.