The only thing RedHat, Mandrake etc have going for them is that they spare a newbie a lot of RTFM. If you really need that, between the two I'd recommend Mandrake, since it both is a notch simpler yet to install and maintain than RedHat, and is designed a wee bit cleaner.

I cannot recommend SuSE to anyone. I have come so far as to say they manage to skewer Linux into a system that is hardly any better than Windows.

But these distros are bloated. If this is for a development only system where you don't care for the multimedia whizbang being set up out of the box, use Slackware or Debian - lean, mean, crazy fast. I prefer Slackware for the insistence on the simplest possible mechanisms everywhere in the distro's design, but a newbie to Unix might prefer Debian for their fantastic apt-* package management tools. There is no better system for binary packages anywhere.

FreeBSD is also a great choice.

Finally, a distribution that deserves more recognition is Gentoo, a Linux with a "package" system which works much like what is known to FreeBSD as the ports - ie packages are all sourcecode that gets automatically downloaded, compiled, tested and installed. The process includes checking for dependencies and recursively resolving them. It's absolutely great if you have the Unix experience to handle the distro (and a fast system to handle a few hundred megabytes of source being compiled during installation). (My only gripe is the SysV style init process.)