I released a Twitter inspired wordpress theme. Free free to check it out at the link above. Here are some feature. It is being actively developed.
Twordder is more of a framework(might be a better term to use) than just a theme. You choose your layout, colors and background image.
Custom Background, Sidebar, Text, Links,and Sidebar Border Colors, Automatically pull color palettes from ColourLovers.com,
Custom Background Image,
Custom Page Width,
Left or Right Sidebar,
Customize Sidebar Width,
Rounded Corners in Firefox, Safari, and iPhone,
Drop Down Menu Support, Facebook Connect Support,
Sticky-Post Class Support,
Widgetized Blog Header,
Footer and Page Sidebar.