Curved is a 3-column, widget-ready theme that sports a variety of features including Top Commenters, Frequent Tags, Twitter, among others.
Geek with Power is a 3-column, widget-ready theme with light colors and rounded corners.
Lovely Rose is a 2-column, fixed-width theme with beautiful header image and static background.
Minimalia is a single-column, minimalistic theme that requires the use of a couple of plugins, which are bundled with the theme.
Lovely Rose already got the best description in its name: lovely! (: