Don't forget Centos and Scientific Linux
To complete the distro-ology of the free Red-Hat flavour, you have to include Centos and Scientific Linux. These are both very close to the corresponding non-free RHEL version. Of the two, Centos tries very hard to be *exactly* the same as RHEL. Scientific Linux has a different kernel, but the differences are slight. Basically, if CERN needs it to do something that Red Hat don't support, then CERN patch their kernel.
As far as ordinary users are concerned, these are both almost identical to RHEL, and the most conservative option you can find. Rock-solid-stable, and still running Gnome-2. The latter is no bad thing, although I've made friends with Fedora + Cinnamon of late. I feel you can be more sure that SL will continue into the future than Centos, because CERN needs SL to stay working.
RHEL 7 is coming soon (months). It will be intersting to see whether CentOS ans/or SL are able to release their 7.0 within 2-3 months, or whether there will be more collateral damage as a result of Red Hat having to protect their commercial interests against Oracle.
BTW, for whoever was berating Fedora for not shipping with non-free software: Fedora is closely linked to Red Hat and therefore has to be VERY cautious when it comes to possible copyright infringement and lawsuits. There are repositories of all the non-free stuff that work well. You have to add them yourself, because Red Hat can't afford the risk even of shipping with them in place.