England's James Wharram started building catamarans inspired by polynesian designs in the 1950s. More than 50 years later, over 5,000 vessels have been built using his plans.
His boat designs cover a variety of sizes and budgets—everything from a 16' outrigger for two to a 46' yacht that sleeps seven. If you've got the money but not the time, there's links to shipbuilders that will construct craft for you.
Interestingly, the company is raising money to build two craft for the island of Tikopia so the locals can continue their 3,000-year old tradition of self-sufficiency.