Fedora is the testbed for Red Hats commercial OS, and where most of the real innovation in Linux happens. It's not really a DIY distribution, things just break down more often than in other mainstream distros (price of living on the cutting edge).
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Major DIY distributions (that are still perfectly usable as everyday systems):
Slackware: Starts you in a fully usable system, stable but everything is vanilla. No distro-specific patches to improve the experience, nothing to get in the way of doing your own thing the old, proper, Unixy way. Tends to drop support even for major projects if those aren't following good development practice (e.g. Gnome). Good for purists.
Arch Linux: Some setup required, very up-to-date software. Base system is clean and elegant, unofficial shortcuts available for almost everything, excellent documentation. Expedient for moderate DIY, and what I use.
Gentoo: Some setup required. Compile most software from source, sophisticated infrastructure to tweak things. Good for heavy DIY if you're willing to put in the effort... I'm not.
