(Second try posting this.. it was up for a little while, then mysteriously vanished!)
Please, please, please, please, please, prettypretty please can we have it???
http://webtreats.mysitemyway.com/free-wordpress-theme-translucence/
And the demo:
http://themes.mysitemyway.com/demo/translucence/?themedemo=translucence-lights
It's got just about EVERYTHING. Custom background, widgets, menu... And it's free!
I think the thing I love the most about it is the balance between the background, and the content, with the content being in an opaque area. The sidebar as semi-opaque is genius.