Boardgames. I met my wife at a boardgame meetup. They're really common in Germany, less so elsewhere but there's usually a boardgame group in every city I've travelled to (all over SE Asia, Central America so far). Perfect for us geeks, too, as the more complex boardgames are really scratching that intellectual itch; learning a new ruleset for a complex game and grokking it enough to create a workable strategy for the game is a great intellectual exercise. And a mix of genders and backgrounds, with conversation during the game, it's a great way of meeting people.