[stomachmonkey]

Depends on what you want it for.

If you are looking for a desktop then Mint.

Redhat is Enterprise, it's gonna cost you $'s, the community edition of Redhat is CentOS.

I run Cent a lot for servers although it also makes for a nice desktop, lags a bit behind on versions of some stuff, PHP is not current but it's stable and has great support.

Personally not a fan of Ubuntu's Unity desktop.

Grab and burn Live CD's of the distro that interests you. You can try them out from disc first then install.

That or grab Virtual Box from Oracle and the corresponding distro VM's and give them a whirl.