Slackware rocks the penguin
Yes, that's right! Slackware is as far as I know the oldest Linux distribution available. If your are looking for a stable, reliable, up to date, highly flexible and last but not least highly configurable Linux distribution - then you might want to give Slackware a try. For those of you already using Slackware no big news.
I want to keep it short here, so only one merrit. I am sure you had the need to port a missing piece of software onto your box. I am also quite sure you had to deal with nasty wizards and configuration scripts part of that distribution, consistently keep trying to overwrite your hand made configuration files. I do not want to mention any other Distro's name here, but I am sure you have had these "pleasures". Well, not with Slackware.
I have to admit, Slackware is probably not the first choice for beginners (Ubuntu is actually a good choice for beginners), but for all of you who want to dig a littel bit more inside.