WinDirStat

This is one of those programs that I take for granted these days, so I didn't think about posting it here until now, but it is one of the most useful freeware programs I have ever found. WinDirStat analyzes your hard drive, and displays both graphically and numerically where your largest files and directories are. I just used it on a laptop at work and found a 15 Gigabyte temp file that needed to be deleted! You can remove files right from the GUI and then refresh the display to reflect the removal. It runs well as a portable too, so I keep a copy on my USB drive. Try it here.

MultiMon Taskbar

This little freeware program, also known as Oscar's Multi-Monitor Taskbar, seems to be the only alternative to the commercial UltraMon. Though it doesn't have as many features as UltraMon, it gets the job done. supporting two to three monitors. It adds a small arrow along with the standard controls in windows and programs that quick-switches the window to the other monitor. Programs appear on the taskbar for the screen they're running on, and there's even a little clipboard history utility on the extra taskbar as a bonus. I use it on my laptop, and when starting away from my docking station, I get a quick message on the screen that I currently do not have multiple monitors, and it quietly exits. You can find it here, along with detailed instructions. While you're there check out Oscar's other free tools.