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Medical tourism is a biggie. Offer an assortment of the best treatments that have been approved by any government on earth. Thus, rich US tourists can take a 1-hour boat ride to get treatments they'd otherwise have to travel to Germany for and vice-versa. (Especially useful if the condition you're treating makes air travel dangerous!) More flexible immigration, licensing, and liability laws means you can use doctors and equipment from, say, India and cut the price of the procedure in half.

Don't forget retreat from the Zombie Apocalypse:

http://zombiesafehouse.wordpress.com/2010-zshc-winner/

Note that these already exist. There's a few retired oil rigs that serve as server farms and mini-states.