Server Live CD
NAS-Like Live CD
aka Damn Small Server
I had a requirement for a small server, not unlike the NASLite products available from Server Elements. Although their offerings were very neat, I found that they lacked a couple of things that I needed - PCMCIA card support and a built-in DHCP server.
Using both the full and DSL versions of Knoppix, I was able to create a small (80Mb) Linux distribution that could boot from CD and satisfy these needs.
The distribution is very basic (as are my Linux skills), but could be enhanced and improved quite easily to suit other purposes (eg DNS, NFS, FTP services etc).
Update June 2010: I'm still getting requests for this :-), so I have uploaded the ISO to my Skydrive account. I have long-since forgotten how it works, or what it required though. IIRC it needs a FAT32 or a Linux-formatted hard disk... But don't quote me on that!
Oh, and there is a boot option 'nodhcp' that prevents the DHCP daemon loading if you already have one on the LAN.