Fedora

I've been using Fedora since Fedora 4, it was my first taste of Linux.
I've tried some other distributions but it is my favorite distro, by far.

If you don't know about Fedora you should definitely check it out:
Fedora Project

There is a new release every 6 months, with the latest in free and open source software, the installation is pretty straight forward, you can choose to set it up as a desktop or server or for development, and they have a great support forum:
Fedora Forum
(You can find me on there posting under biggsk)

If you have time leave me some comments on what your favorite distro is and why.