Use Google to search for a version of Linux that can be run from a CD, or search the Linux forums, here
It's been discussed several times.
Just search for "live Linux"
Here's one topic that discusses the different versions of live Linux:What Is Your Favorite Live Linux?
Once you find the distro you want to try, you'll need to burn an ISO image to CD.
Instructions for that can be found here:How to write / burn an ISO or CD/DVD image
A standard CD will work.