LiGurOS is a source based distribution building upon code and packages from a broad family of Gentoo-based distributions. Source based means all the software is compiled from source. The Gentoo-family of operating systems heavily uses portage as the package manager with the ability to change settings globally but also per package. So you can specify what exact configuration options are passed to the package upon building. This results in a operating system without bloat and running optimized for your processor.

Pentoo is a Live CD and Live USB designed for penetration testing and security assessment. Based off Gentoo Linux, Pentoo is provided both as 32 and 64 bit installable livecd.

Repology, the packaging hub.

Repology monitors a huge number of package repositories and other sources comparing packages versions across them and gathering other information. Repology shows you in which repositories a given project is packaged, which version is the latest and which needs updating, who maintains the package, and other related information. Repology might be useful

Calculate is a fast and functional user-friendly Linux distribution, based on Gentoo and still backward compatible with it. It maintains an optimal balance between state-of-the-art and stability, providing the latest versions of applications and stable versions of libraries. As Calculate Linux is a rolling-release distribution, you install the system once and update it throughout the life of your hardware.