Ambiance and Radiance fixed for custom button layouts.
I had to redo all of Radiance’s buttons (and fix them along the way, mind you), but it’s here: both themes now support changing the order of the titlebar buttons.
I also tried to fix some inconsistencies that creeped up in Radiance’s gtkrc, namely Nautilus’ breadcrumb bar.
Following Umang's idea o Launchpad, now the menu button background is fully opaque and most button layouts should work fine now (see screenshots).
Note: you’ll need to add a PPA to your software sources in order to get the dependencies for this package. Please look here for instructions: http://http://www.webupd8.org/2010/03/ubuntu-lucid-light-themes-radiance-and.html
Note: Sorry for not uploading the package directly to GNOME-Look.org, but their submission form has a bug that hasn’t allowed me to do so. Google Docs’ll have to do.