The Envato Marketplaces allow anyone to buy or sell digital goods like WordPress themes, stock audio, After Effects project files, Flash templates and much more. The marketplaces are home to a thriving community of over 240,000 users, authors and buyers and everyday hundreds of new files are added.
Check it out:
HTML templates: http://themeforest.net/
Flash Components: http://activeden.net/
Music and Audio: http://audiojungle.net/
After Effects: http://videohive.net/
PhotoShop and Vectores: http://graphicriver.net/