How about making tee-shirts that say:
"I got my free bitcoin from www.freebitcoinsite.com/1fj94
Where that web address is unique, leads to a page that hands out a free bitcoin, and the shirt has a confirmation code on the tag or someplace inconspicuous so that no one else could claim it?
Not only would it advertise bitcoins, but as handouts, they would be great, because it would let the person know that they can get started in the currency for free.
Said web address should also offer up ideas of how to spend the free bitcoin and how to buy more of them.