Gentoo Portage was inspired by BSD Ports. It has many outstanding features:

• a single tool (emerge) to update the tree, install/deinstall/upgrade packages and carry out most other tasks
• slots allow several versions (branches) of one package to be installed simultaneously
• masking - built in support for specification of supported build environments
• USE flags
• built-in distcc/ccache support
• build packages without installing them
• one of valid licenses in the ebuild
• ebuilds are shell scripts that set variables, call and define functions
• lots of helper functions, like enewuser and edos2unix
• some support for FHS
• eclasses - collections of macros
• great documentation
• can run on many Linux/BSD/Solaris systems