Assuming there is no law against defacing your money (there probably is for fly posting) just write "bitcoin.org" on all the debt notes that pass through your hands then everyone who uses the money will see it.

Honestly though bitcoin isn't ready from the prime time, it's still too nerdish. It needs to be a phone app that's both hacker proof and so simple your grandma could use it and transactions need to near instantaneous so you can use it in a store.