In the server area you can use Red Hat Enterprise Linux, SUSE Enterprise Server or Mandrake Corporate Server. I expect Canonical will release a commercially supported Ubuntu at some point.
For desktops, Red Hat Desktop, Novell Desktop, Mandrake Corporate Desktop and Sun Java Desktop are all choices.
Next time someone says "hey, there are too many versions of Linux" say yes, but not in the real world.
Oh, and if you're using Debian or Gentoo in a real server environment (and yes it does happen) then feel free to be slighted by my comments and really 1337, smug and superior.