Which one, and why?
Or, if you don't currently use Linux, which ones have you looked at or thought about trying?
Slackware.
I'm about to switch.
I tried the LiveCD for Bisexual Ubuntu Linux. It seemed pretty nice. I'm switching to Kubuntu (KDE version). I assume I'll switch to something else later, since I won't really know enough to make an informed decision before I've actually used Linux.
I view it as a horses-for-courses market...
For my own machines, and boxes I manage -- Gentoo Linux.
* It runs on all my machines... both x86 and MIPS
* Great package management
* Lets me do everything, my way.
* Install only the stuff you need, no unneeded cruft.
* I also happen to be a developer for Gentoo -- so this is a no-brainer. ;-)
For other people's machines I'm setting up -- Ubuntu
* Great package management
* Well integrated desktop
* Keeps things simple, but allows users to get their hands dirty.
I also dabble with Debian (I have one box currently running Debian, an old Toshiba Satellite PRO 430CDS -- acts as my serial console server).
4-ch is powered by Debian. That's not something we like to brag about: given that the Debian community is reknown for being a bunch of anti-social idiots who like to beat up the n00bs. But the OS has a "No Bullshit" policy of only installing what is needed, without having to build everything from scratch. And with the performance we get out of it, this is a good thing.
A good laugh: http://nanocrew.net/2005/10/03/despair-linux/
I use Ubuntu on a laptop; the April 2005 version. It's mostly nice, but that "Synaptic" program is so totally broken: slow, horridly organized...
Has that been improved in the October 2005 version? If so, I might bother trying to upgrade.
Gentoo.
I do not recommend Gentoo. The ricer speed boost is minimal even with lots of flags, and binary packages are nonexistent. The BSD-style services are nice but still a hassle compared with (yes) Windows. The only reason I use it is because I managed to get my fake VIA graphics card working on it, and I don't want to waste countless hours of my life duplicating that effort on a better distro, when I could be posting on Internet forums.
I've never tried Ubuntu, but it sounds nice, and Debian was fun.