They raffled off prizes, including autographed photos and some Alliance money that was actually used in the movie! It seemed to me that the props needed to be mine, so femetal and I pulled a Lazlo Hollyfeld and bought an absurd number of raffle tickets. It is for charity, after all.
Well, we didn't win the cashy-money (*pout*), but we did walk away with 10 of the prizes, including a not-available-in-stores mousepad, a rather nice Browncoat bag that I'll probably use at 'con, and a bunch of other stuff. :-) zensidhe got the autographed photo of Summer Glau, which conveniently comes in a waterproof cover. Enjoy it, bro. ;-)
Of course, His Whedon-ness was aware of the event, and has expressed his gratitude to the fans in typical Joss fashion. Shiny!