Frugal

Frugal isn’t your typical WordPress Theme. It’s not just a cookie-cutter template to slap on the face of your site. Frugal is more of a design platform. It gives you the power and flexibility to create a site that’s uniquely yours. With over 600 custom options at your fingertips, what you can create using Frugal is only limited by imagination.

Hybrid Core

Hybrid Core is a WordPress theme development framework for creating solid parent themes. It allows theme developers to forget about all the complex functionality and dive straight into coding their theme’s HTML, CSS, and JavaScript.

This framework’s code is completely free and open source. You can use it for creating publicly-downloadable themes, client work, or even a commercial theme business.

Thematic

Thematic is a free, open-source, highly extensible, search-engine optimized WordPress Theme Framework featuring 13 widget-ready areas, grid-based layout samples, styling for popular plugins, and a whole community behind it. It’s perfect for beginner bloggers and WordPress development professionals.

Thesis

The Thesis Theme for WordPress is a premium template system designed to serve as the rock-solid foundation beneath any kind of website.

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.

Headway

Headway is a great framework that allows non-designers the chance to make an attractive looking website very easily. With a built-in Visual Editor, and a friendly and very helpful support community, Headway is shaping up to be a very tough competitor in the Framework world. Headway also has top notch search engine optimization, custom css/php options for developers, and a configuration panel that makes creating a website a snap.

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.

Carrington Build

Creating custom WordPress page layouts with Carrington Build is as simple as drag-and-drop. By adding content Modules and WordPress sidebars and widgets you’re free to create any page layout you can possible imagine.

3.0 Basics

This WordPress 3.0 based theme is a free theme that is the perfect starting point for theme developers making a new theme. It has many common features used by plugins built-in as well as a pre-made custom post type that allows you to build a site where you or your users can post links to your favorite sites, which will automatically generate a screenshot image of the website to be displayed on the page.

Builder

iThemes Builder is a powerful, flexible, easy-to-use WordPress theme designed to allow you to quickly build websites and blogs with WordPress. With Builder’sinnovative Layout Engine, you can build almost any layout you’d like within minutes. Then bling out your site with graphics and styling.

Hybrid

Hybrid is a free, open-source theme framework.

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.