Premium Wordpress themes are available for purchase and download to any blog built on Wordpress.org. Premium themes are a great choice for people who want to give their blogs a custom look (more so than the free themes that come pre-installed with Wordpress or offered on sites that list free Wordpress themes) without spending a lot on custom design. Take a look at the sites below which are all well-known and well-respected in the Wordpress community for creating great premium Wordpress themes.
Read a review of the iThemes FlexxTheme.
Read a review of the Revolution theme and view a visual overview of the Revolution theme.