An Emerald theme to match the Greybird theme:
http://xfce-look.org/content/show.php/Greybird?content=142534
which is the default theme of Xubuntu 11.04
I slightly modified "elementary 2k10":
http://compiz-themes.org/content/show.php/elementary+2k10?content=121543
Thanks to the author.
Ochosi from the Shimmerproject informed me of the release of the official Greybird.emerald theme, enpacked with the GTK theme. Thanks to him for his work.

Ochosi:
http://xfce-look.org/usermanager/search.php?username=ochosi

the Shimmerproject:
http://shimmerproject.org/project/greybird/