I have just posted a link on our gnuraido.org Build Guide webpage to a one-step installation script for GNU Radio on Ubuntu and Fedora. The script was built by Marcus Leech and is hosted from his website, so thanks Marcus!
http://gnuradio.org/redmine/wiki/gnuradio/BuildGuide
This scrpt is designd for Fedora and Ubuntu. Specifically, Fedora 12 to 15 and Ubuntu 9.04 to 10.10. I have made it work under Ubuntu 11.04, and expect the script to be udated shortly for that OS version.
Marcus feels, and I concur, that the majority of GNU Radio users use Fedora or Ubuntu, so this script can make it easy for a large portion of our user base to quickly and easily install GNU Radio and all of its dependencies.