A very minimal and slick Emerald theme, based on the LittleGlass theme by lassekongo83. This theme uses a dark glass border instead of light, and goes well with the HumanLogin controls from Ubuntu 10.04, or another dark Metacity theme. Buttons are on the left.
From the Gnome theme chooser (Settings->Preferences->Appearance), choose a base theme and then click "Customize...". Select HumanLogin controls.