pss 04/06/11 - This was one of first 5 posts on Nature ID. I originally posted it as an unknown moth. Thanks to the help of Chris Grinter of the Skeptical Moth, I now have corrected the ID above with embedded links.
From my days of butterfly monitoring in Ohio, I always found Euphydryas sp. (Baltimores in OH) to be "friendly" and extremely cute with their brightly colored antennal clubs. They are voracious nectarers, don't seem to mind being touched or held, and will often follow you down the path.
True to its "variable" common name, this butterfly's appearance is highly variable with a top view that can range from predominantly black to predominantly orange. It doesn't help when seeing them on the wing that the underside is equally patterned and gorgeously orange. Larvae feed in Indian paintbrushes. There's a slight chance this one is Euphydryas editha, but in other pics I think I can see white spots on the abdomen. Glassberg says Edith's checkerspots are often impossible to distinguish in the field from variable checkerspots.