From Wired.com, May 18th:
Technologists have long dreamed of a clickable world, where machine-readable tags link physical objects to the universe of information on the Web. That dream came closer to reality this month with the release of Semacode, a free system that lets camera phones convert bar codes into URLs.
From Smart Mobs by Howard Reingold (pp. 91-93), a must-read book.