Green

Where’s George. This is a pretty interesting site. You register some American/Canadian bills under your account, then write the website URL and some instructions on the note. Let it loose into the wild (spend it, drop it, give it, whatever) and wait for people who receive this note to post followups. See what interesting places your notes end up it… XD Read their top 10 entries.

BookCrossing uses the same tracking concept, except for books.