I always thought it was easy to identify poison ivy. Three leaves, red-tinged, waxy appearance. But this site has set me straight. "Poison ivy is so adaptable that it grows under very different conditions, so it shows up looking different ways." Be sure to check out the gallery of rash photos, especially if you enjoyed the pics of my ringworm. Link (Thanks, Stefan!)
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.