Have you considered authorising a company somewhere to produce real-world badges for stackoverflow accounts?
Obviously this is trivial, but I'm sure a few people (myself included) would enjoy being able to bring our... flair... into the real world.
The benefits are both ways; it advertises SO in the real world (at meetups, conventions, any kind of technical gathering), and allows people to show-off their status, which is, of course, one of the defining traits of geekdom.
Edit: Could we have stackoverflow at cafepress, or somesuch? So at the very least we can get stackoverflow branded stuff? Is the artwork available as vector anywhere?