I run Slackware 11 on my development server.

I've heard lots of people who think CentOS is a great way to go. Of course there's also ubuntu, fedora, too many to name really.

I'd be interested to know what HostMySite's customers are running, at home or at work!

I've always been more of a fan of Debian based distributions than redhat based ones. for my home uses, I've always been a fan of apt. I was using debian etch, but I've recently switched to Ubuntu. Debian's a great base system, and Ubuntu seems to be doing a good job of refining for the desktop and really focusing on the desktop user. it'll be interesting to see what happens in the future with upstart, and the X graphical configuration utility.

I've also used Gentoo on some of my desktop machines, and currently run it on the computer I use at work. For people who are willing to fiddle around and put some work into it, Gentoo is great. Not so much because you can get a lean kernel and system (I think sometimes the improvement benefits cited by pro-gentoo'ists are a little inflated), but because doing a stage3 install really teaches you more about the underpinnings of your Linux distribution, and is a great teaching tool, if you're willing to put in the time.

Emerge might be overkill for most desktop users, but I think it's tremendous as a server package management system. I've recently switched most of my personal servers over to gentoo, and as a whole I love the distribution.

So, Debian/Ubuntu and Gentoo are what I spend most of my current time using.

I have found Red Hat Enterprise or CentOS to be the best fit for most of our customers (and myself).

I stay away from Fedora, as it is a testing platform with a very short life-cycle (~1.5 yrs.) vs. the enterprise life-cycle of RHEL/CentOS.