I see quite a few Cargo Bikes (XtraCycle.com) Long Tails chained up outside of hipster havens in DC. Look sort of goofy, but really practical if you live in the city and don't own a car.

EDIT: I actually see the Cargo Bikes/Xtra Cycles Free Radical Bolt On extension a lot more than the Long Tail. I just poked around the site and saw that Long Tail is a complete bike and Free Radical was bolt on