I have jumped around through a few Linux distros in my time.
So far I've yet to find one that makes me as happy as FreeBSD in terms of package management, which is fairly important.
1) Arch Linux -- I like that in theory they offer both binary and source options like FreeBSD, but it's very immature -- the system is extremely awkward if you go source and (silent) broken dependencies seem very common. Overall, Arch is good in theory but needs ~3+ years before it is mature.
2) Debian. Debian was how I found out that I hate binary-only distros. Lasted about 6 hours on my machine.
3) Gentoo. Gentoo would be a lot better if I had a tinderbox or a faster processor, but at 1.6GHz I'm wasting a lot of time. Portage is good but not great. Very few binaries (outside of OO and Firefox) and upgrading frequently silently breaks dependencies, which is a big pet peeve. It's what I currently run. I'm less than satisfied, though.
4) (K)Ubuntu. We run this at work. I like that everything Just Works(tm). This is what I recommend to all Linux noobs. The KDE interface is less intimidating for people who are migrating from Windows. I'd never run it on my home machine though, because as I said I hate binary-only package systems.
5) Slackware. This is the next one I need to try out. I hear a lot about it and have never loaded it up. It'll probably eventually replace my Gentoo after I back Gentoo up (I am *not* rebuilding that from scratch on this slow processor
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