Of all of the distributions of Linux I have tried, Ubuntu is by far the best contender, IMO.
However, let me advise you in advance that running the O/S from a CD is very, very, slow and also, in ways other than the slow performance it does not give you a realistic picture of what Ubuntu is really like.
My advise would be to, if there is any way you can see your way clear, actually install Ubuntu on the hard drive.
You can either try the currently RELEASED version named Breezy Badger 5.10 or you might want to try the lastest BETA release of Dapper Drake. Dapper Drake is supposed to be RELEASED about June 1, 2006.
Good luck.