There is also Zero Install, "The antidote to app-stores" : http://0install.net/
Zero Install is a decentralised cross-distribution software installation system. Other features include full support for shared libraries, sharing between users, and integration with native platform package managers. It supports both binary and source packages, and works on Linux, Mac OS X, Unix and Windows systems.
It solves many problems and limitations of the native package managers, especially for higher level apps. Applications packaged that way can be made to work in any distro, and this is important because we can't force all Raspberry pi users to use the same distro in order to download official packages.
And you don't need a centralized control like an app-store or distro repository. Of course, search engines and reference repositories are welcome on top of it.
Sugar project (originally for One Laptop per Child XO laptop) seems to be experimenting with zero-install as basis for their package system: http://thread.gmane.org/gmane......devel/4627