You can't really do anything like"apt-get install http://example.com/foo/bar-2.7"; or "apt-get install./private-package-that-joe-sent-me-via-email".
You can. Debian is weird though because it is done via dpkg, not apt-get. In Arch it is as simple to "pacman -U package-file" vs "pacman -S name-in-repo".
