Ambiance, the default Ubuntu theme, will get a dark toolbar very soon. The news comes from Andrea Cimitan who has posted a screenshot on Google+:
If you want to use Ambiance with a dark toolbar already, you can use Ambiance Evolution, an unofficial version that already has a dark toolbar - see THIS page for more info.
In other Oneiric news, Compiz was updated today and the modal dialogs finally look like they are supposed to for Unity 3D:
Previously, the modal dialogs had a regular window titlebar in Unity 3D.
First screenhot thanks Andrea Cimitan @ Google+, via chimerarevo.com