To install the development version, which has the benefit of up to date applets and code, install the appropriate apt source, sudo apt-get update, and sudo apt-get install avant-window-navigator-trunk awn-manager-trunk awn-extras-applets-trunk:

deb http://ppa.launchpad.net/awn-testing/ubuntu hardy main
deb-src http://ppa.launchpad.net/awn-testing/ubuntu hardy main