While lots of people have made money selling t-shirts over the years this guy has a pretty original concept. Customers pay his company to wear t-shirts bearing their message. They can buy a single day or multiple days of advertising and the cost goes up as the year goes on. In addition to his staff wearing the shirts, the company posts YouTube videos and supplies mentions in live video shows as well as exposure on their homepage and calendar. Simple and straightforward, while not for everyone this clever concept is catching on.
Check it out: http://www.iwearyourshirt.com/