From Scot's newsletter, I found this:
The idea is that you burn these utilities to a CD to have ready in the event you run into trouble with your computer. So when your drive tanks and you can't access your data, you still have the tools at hand -- on a CD instead of your cooked hard drive -- to fix it. You'll find tools that help you with hard disks and partitions, file systems, memory, system utilities, DOS boot disks, Linux boot disks, and more. All are available singly (from their maker's sites) or in the full Ultimate Boot CD collection.
Very cool. I don't need it so much these days since my machines don't change much, but wow this could have saved me a lot of time in the past, as an admin or as a speaker at conferences when invariably, something goes horribly wrong with your demo machine the day before the talk.