WPStartbox

StartBox is a great theme framework for WordPress. It comes with an incredibly easy-to-use, modular settings page. For users, this means a quick and painless setup for your website, for theme authors this means an incredible new level of control for your themes.

ChildThemes for ClassiPress

ChildThemes for ClassiPress, the most popular and widely used classified ads software for WordPress.

Genesis Theme

This is a WordPress 3.0-ready theme and is SEO-focused. It’s incredibly extensible with the use of hooks and child themes. Also, widgets can go in various places besides just the sidebar. This theme also integrates with BuddyPress, which is great if you or your clients need an open-source social networking solution your WordPress site.

Geneva

A clean, simple grid-based portfolio theme that displays your posts in attractive thumbnails.

Atahualpa

A 3 columns fluid WordPress theme.
3 columns, fluid 100% width with customizable sidebar widths
Changeable logo and header images
Widget ready
Options page with Auto SEO options

Carrington Theme

Carrington is a CMS theme platform for WordPress that makes it easy to create unique looks for different categories, post types and comments just by creating custom templates.

Clean Slate

A minimalist yet stylish theme for any type of site. Thoughtful design matched with flexible theme options makes this a perfectly balanced theme for any project.

Coda

Coda by WooThemes

Suffusion

An elegant, versatile and browser-safe theme with a power-packed set of options. It has 19 widget areas, one-column, two-column and three-column fixed-width formats, 10 pre-defined templates, 17 pre-defined color schemes, two customizable multi-level drop-down menus, featured posts, a magazine layout, tabbed sidebars, widgets for Twitter, Social Networks and Google Translator, translations in many languages and RTL language support. WP 3.0 Menus, Custom Post Types and Custom Taxonomies are integrated. A BuddyPress support pack is available on the theme page.

Hybrid

Hybrid is a free, open-source theme framework.