(EDIT Sep, 2010: now with updated packages, see below!)
Running Debian Lenny on my Acer Aspire 5572 notebook I wanted a more "up-to-date" look for it's Gnome desktop. As I recently came across some screenshots of Ubuntu's upcoming release "Lucid Lynx" with it's new GTK theme I decided to give it a try (you have to get used to the buttons being on the left side of the windows, though! ;-) see screenshot below). Of course, the new Ubuntu Mono iconset goes very well with this theme, so I needed that, too.
To make everything work in Lenny, I grabbed all the source packages from Ubuntu's package repository and then made deb packages for Lenny from them. I also replaced the Ubuntu logo within the two icon packages with Debian's logo.
The new Ubuntu "light-themes" (Ambiance/Radiance) need the latest murrine engine, which of course isn't included in Lenny. So, this was the first thing I took care of. This is the only package which is architecture dependent and I can only provide it for i368. If you need murrine engine for amd64, do as follows: