Gentoo is among a hand full of distro's who have dared to move away from RPM or DEB format and still be able to make a mark of thier own.

as per wikipedia

The Gentoo Linux operating system (pronounced /ˈdʒɛntuː/) is a Linux distribution based on the Portage package management system. The development project and its products are named after the Gentoo penguin. Gentoo package management is designed to be modular, portable, easy to maintain, flexible, and optimized for the user's machine. Packages are normally built from source code, continuing the tradition of the ports collection, although for convenience, some large software packages are also available as precompiled binaries for various architectures.


AND no one can describe it more better.

Its portage system is its disadvantage coz newbies get scarred by its tech word usage, and in the meantime its a paradise for veteran's as they can have a custom compiled per system optimized code.

Site : http://www.gentoo.org/

documentation : http://gentoo-wiki.com/

download : http://www.gentoo.org/main/en/where.xml