You've probably seen The League of S.T.E.A.M. on Boing Boing before, as both Cory and Xeni have posted their videos. In addition to videos, they do interactive live performances at parties across L.A.
The basic premise is that they hunt supernatural creatures with steampunk-inspired gear. If you see them at an event, they usually have a few display tables set up where the League will demonstrate how their props work. They'll also take partygoers on ghost hunts or chase after vampires throughout the venue. I've seen the League perform a handful of times over the past year and it's always a good time. They've appeared at nightclubs and Comic-Con parties as well as their own events. For those who will be at Dragon*Con this year, the League has a short in the convention's film festival.