Of all the open projects out on the Internet, this is one that is most valuable to anybody who has to deal with hardware:
If you deal with hardware on a regular basis, you really ought to have at least three copies of this burned and handy. Even if you don’t deal with hardware on a regular basis, you should know about this site. Trying to acquire equivalent functionality out of commercial software would cost you an arm and a leg. Maybe a bit of spleen as well.
Edited to add [19-May-2008]:
Instructions here on how to make an Ultimate Boot CD… on a USB stick, instead of a CD drive. Obviously useful if the CD drive is not operational, or because a USB stick is pretty easy to carry around, while CD’s don’t exactly fit in your pocket.