Link to editable PDF
Update: Here's another, from Scott Shanks.
Update: Another set, from FINK.
Link to Adobe Illustrator file
Update: A stencil friendly version, from pATCH, who says: "I endorse nothing illegal, but graffiti is beautiful."
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. His new book is Maker Dad: Lunch Box Guitars, Antigravity Jars, and 22 Other Incredibly Cool Father-Daughter DIY Projects