gentoo
Ah, Gentoo. An extremely powerful Linux distribution, that quite frankly, is really cool.
Intro
Let me being not by telling you what Gentoo is, but rather compare it to one of the most popular Linux distributions today: Ubuntu. Ubuntu has been widely hailed as the average user's Linux, a CD that installs painlessly and "just works." Well, Ubuntu has made a large impact on my computing life, introducing me to Linux and all its possibilities. However, power users and tinkerers will always wonder: is there more? The answer is: yes. Gentoo Linux is almost the polar opposite of Ubuntu; it needs a lot of work to get going and doesn't have that "just works" aspect to it. However, if one takes the time and effort to learn what's going on, Gentoo can turn into one of the most powerful environments to work in.
What's so special about it, anyways?
The beauty of Gentoo lies in the fact that everything comes from you, the user. From the very start, the installation process involves downloading a tarball, or archive, of a very simplistic Linux system. From there, you set various configuration files to control how your computer will work. Major configuration options include Xorg setup, compiler options, and adding users, all of which are usually handled automatically in Ubuntu. However, this ensures that the computer will have only what you've decided to have on it and work precisely at its peak. Anytime you want to install a program, you have to compile it, which means that the source code that the program's developer wrote is going to be downloaded, then transformed into a program. During this process, various optimizations are applied to the code so that they'll run even faster. Heck, even the kernel is compiled only with the options that you select. That is the power of Gentoo.
Sounds cool, any downsides?
Well of course there's downsides! Before you go off installing Gentoo on every computer you own and come crying to me that they're all broken, keep this in mind. Many many many bad things can happen. When you muck so low with the system, things are bound to break. Only use Gentoo if you have a strong stomach and you actually like breaking things, learning, and living on the cutting edge. If you want a "just works" approach, use Ubuntu, or any of the other fine Linux distros out there.