Installing on Arch Linux
GNURadio can be installed easily from the official Arch repository using pacman.
sudo pacman -S gnuradio gnuradio-companion
There are many additional packages like gr-osmosdr that brings extra hardware support in GNURadio.
sudo pacman -S gnuradio-osmosdr gnuradio-iqbal gnuradio-fcdproplus
The official package doesn't have qtgui features enabled by default (will be enabled in future). GNURadio with QT support can be installed using "gnuradio-opt-git" package from AUR. This package will install GNURadio to "/opt" and can be used in parallel with other GNURadio installations.
If you have never built & installed an AUR package before, the AUR wiki page gives excellent instructions:
Installing Packages from AUR
Installing GNU Radio from AUR
If you don't use yaourt/pacaur or something of the likes do the following:
Go to http://aur.archlinux.org and search for the package "gnuradio-git".
Download the tarball (gnuradio-git.tar.gz) on the packages page.
$ tar zxf gnuradio-git.tar.gz $ cd gnuradio-git $ makepkg
This should build, and leave you with a file like gnuradio-git-20111025-1-x86_64.pkg.tar.xz which you can install via
$ sudo pacman -U gnuradio-git-20111025-1-x86_64.pkg.tar.xz
In case you run into trouble building GNU radio using AUR leave a message on the AUR page.