@memed:
Knoppix is very cool and I'm using it for some of our desktop systems. For servers I go with plain Debian.
Debian has three main trees: stable testing and unstable.
Use "stable" for production systems. Some of the packages seam to be outdated by newer releases but all known bugs get fixed first in this release. For instance the backported all kernelfixes (do_req bug) to the 2.4.18 kernel. The only drawback is that no new features will be added to "stable".
If you need more current releases (or new features) try the "testing" tree.
And if you want have your hands on the latest developments "unstable" is you choice.
The best feature of Debian (and Knoppix) ist the "apt-get" utility (don't use dselect or tastselect to install new packages as they install a lot of unneccessary stuff). "apt-get update" updates the list of available packages and "apt-get dist-upgrade" upgrades your system to the most current version of the selected tree. And installing new programs is also simple: "apt-get install apache"! Well, sometimes it's hard to guess the right package name (libstdc++2.10-glibc2.2 provides libstdc++-libc6.2-2.so.3) but that is the same for other distributions
.
Feel free to ask me if you get stuck with debian/knoppix at some point
