Ubuntu Lucid (10.04) Light Themes (Radiance and Ambiance) – click me if you haven’t seen the themes yet – will probably be updated lots of times until Lucid Lynx is released. More here

If you don’t use Lucid Lynx yet, you probably still want to upgrade to the latest version of the GTK and icon themes constantly to see what’s new. For this reason, we’ve packaged the latest “light-themes” and “ubuntu-mono” (the icon pack) in the WebUpd8 PPA and we will update them as soon as new version of these themes are released.