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!
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.