The Bisigi Project provides 13 well-rounded themes for Gnome on Linux. The project focus is Debian/Ubuntu, but I installed most of the components of the Infinity theme on a CentOS 5.3 machine. You just have to download the .tgz file, extract it, and install the theme components manually. It’s great to see even more attention paid to the Linux user interface. Each year, there’s less of a reason to choose a non-free OS and the beautiful interfaces on Linux are a big part of that.