Elive is another interesting distribution that has just released an unstable development release you can download and try without installing it on a hard drive. If you are interested in trying Enlightenment without installing it, this is a natural choice for you.
Elive is based on Debian. Its minimal requirements are very minimal: a 100 Mhz CPU and 64 MB of RAM. To be honest, the minimum recommended hardware is 300 Mhz and 128 Mb of RAM. Still, nothing fancy is needed for running Elive.