I’ve always found gnome desktops to be something of a hassle to find good themes for. Usually it takes a solid amount of time rooting around in one of the repositories, checking compatibility, etc. etc.
One of the places I’ve found that has a reliable theme pack that’ll install and give you a clean looking desktop to work with is the Bisigi Project. Just pop their repositories in your system, install, and go.
Gnome 3 support is coming with the release of Ubuntu 12.04. For now you can hack it in for previous versions of gnome or get it working with LXDE.
No idea what happened to the themes. Apparently they’ve disappeared all these years later.
Sad as they really were quite good.
And you can find them at launchpad: Bisigi Gnome Themes (old) at Launchpad