Fedora

I'd like to become more familiar with Unix. To that end I want to install and practice/play with a (open source) Unix distro; however, I'm uncertain which one I should use. I'm considering freebsd, openbsd, and openSolaris.

I'm familiar and comfortable with RHL/CentOS and Debian/Ubuntu. Keeping the aforementioned in mind, I'd appreciate recommendations on which distro I use. Thanks.

As always with those questions: it depends. What skills do you want to learn? What direction do you want to go in your job? Do you want to use the installation for everyday, or for a server? A firewall?

I'm primarily interested in becoming familiar with installing and configuring softwares like svn, mysql, apache, etc. on unix thus creating a development box. Also, I'd like to use the installation for everyday use as opposed to a server that is set and forgotten. Essentially, I want something easy to use and learn with; for example when I started learning linux I started with Ubuntu which was very easy to use and practice with and once I got comfortable I was able to move on to RHL & CentOS, which I now prefer. Also, since this installation is primarily to learning/practicing it will be put on an older machine, so I'd prefer something that isn't going to be a pain to get up and running.

Older machine + development + learning/practice: I'd say Fedora (since you already know RHEL/CentOS), Debian (base for Ubuntu, largest repo of all distributions), or something completely different like Sabayon (source-based distribution), Arch, or Slackware/Slax.