In a span of less than a week, Linux distributions get its timely update with the release of the following versions:
1. Freespire 2.0
2. Mandriva 2008 Beta 1
3. Ubuntu Gutsy Gibbon Tribe 4
4. MEPIS KDE 4 Beta 1 Live DVD
With the exception of Mandriva, I think that all the others are either based on Ubuntu or Debian (which Ubuntu is based on).
Take your pick. As for me, I am testing OpenSolaris now.