My friend Matt Richardson made a system for his bike that projects a spotlight with data onto the street. It's currently set up to display speed, but it can also be used to project other kinds of information (like turn-by-turn directions). He's going to write about it for MAKE so you can build one, too.
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. Come and hear Mark speak at the ALA conference in Chicago on July 1.