Ubunto, no. Damn Small Linux, Puppy Linux, Freeduc, Knoscience, and Kioskcd (to name but five distros), yes. Not all flavors of Linux require large amounts of memory or terabyte-speed processors to run. Some live-CD distros can even boot your machine and allow you to rescue critical files after winDoze crashes and renders your machine inoperable. There is even one specifically tailored to rescue your system, as well as repartition your hard drive and make images of the partitions for future rescues. Makes recovery a lot less painful if something corrupts your system. :)
I have a script here that allows you to combine multiple live CD distros onto one DVD (or CD) disc.
Latest is Tiny Core Linux 1.4
Developer was heavily involved with Damn Small Linux (there) but got little credit ...story on Distrowatch..
It appears that development has stopped on it. V2.8 is available for download, with posts in the blog about better hardware support in V3.x. That was in ~2007.
I tried it on a Dell Optiplex GX280. It won't see the Broadcom NIC. *shrug*