Two column theme ready for WordPress 2.7 with customizable backgrounds, paged, threaded and nested comments.
Sacred Blue is a clean two-column and widget-ready theme sporting a bright color scheme. It comes with an options page where you can customize various features of the theme like the Ads, Navigation menu items etc.
QuickPic is a 1-column, widget-ready, SEO-optimized, Ad-ready, compatible WordPress theme which is very useful for all types of bloggers, in particular for photobloggers.
Two column theme with a beautiful sun header, widgetized sidebar, threaded comments support. Compatible with WordPress 2.7.
Miniflex takes advantage of the footer for the widget enabled sidebar. This one column theme is clean with few colors, nice little features and the use of typography to make it more elegant.
Fixed width, two column theme with support for comments threading (WP 2.7), comments paging (WP 2.7), gravatars, post tags, sidebar widgets
Old School is a child theme of the Hybrid theme framework. It takes advantage of WordPress 2.7′s new features such as threaded comments, but it’s also backward compatible with WP 2.6. It has an additional page template with a tabbed and widgetized feature section along with a tabbed category section. It also has two widget sections: Sidebar and Footer.
Fixed width, two column, adsense and gravatar ready with custom header images
The WordPress theme is 3 column, widgetized and header image can be changed to adapt a lot of variations. The theme is also cool to set up PhpBay stores.
You may also want to check out Blogsessive’s 20 Free Corporate WordPress Themes.