Man, Knoppix is cool! If you need a rescue disk or anythink like that, Knoppix is the way to go.
I saw a lot of posts suggesting it on this site, but my only experience with a CD-run distribution was DemoLinux, and I wasn't that impressed. DemoLinux did what it said: it runs Linux from CD, but that's all it did. Knoppix has all KINDS of applications, multiple window managers, and the hardware detection rocks (only distro to recognize my USB 2.0 CD burner out-of-the-box).
In other words, I'd seriously consider installing it permanently on my machine (if I weren't so busy with LFS