I think an IT tech wanting just to experiment with using Linux would want to try a popular LiveCD -- if not Knoppix, then the very popular Ubuntu. If he knows something about Linux, however, he might like carrying NimbleX around to solve network problems. This 200MB,Slackware-based version will fit on an 8cm CD (but alas not on a CD business card -- remember when LinuxCare passed out little rescue disks like that, back in the previous century?), or on a thumb-device on a keychain.
With it, a sysadmin can access the network and data on remote machines, install it over the network and touch a good many things. Here's a list of what Nimblex can do is up at their site.
Depending on the size of memory device that you carry, you can add your favorite trouble-shooting and repair tools. If you want to test security as well, then you should look into PHLAK to see their penetration-testing LiveCD.
This was first published in March 2007