The book, "Linux in a Nutshell" is a great resource for Linux commands.
To really learn the Linux OS then I suggest you install a 'general use' distribution like RedHat, Mandrake, Debian, Slackware, etc.
If you are a Linux newbie then try RedHat or Mandrake first. Or Slack if you are wanting more of a challenge. It will be harder, but you'll probably learn more. IMHO Debian is a hard climb, but it's supposed to be the hot-rod power-tool.
You can install it on a 486 or low end pentium and still have enough power to learn the OS. If you want to use it as a desktop OS then you'll need more RAM and CPU.
If you are using e-smith for anything but a test box then I strongly suggest that you do this. You don't want to fry your production box playing around with Linux.