ThemeForest, and the entire Envato Marketplace family, has changed the way many build, access, and approach web construction, design, and extension. It’s a win-win, for users and designers, developers and owners.
In their words, you can begin your search for:
Site templates and themes to skin popular CMS products like WordPress, Drupal and Joomla, starting at $5.
It’s a great place to start for WordPress Themes, and I recommend it.