Right now there's some footage from the Showest convention in Las Vegas where the theatre owners get wooed and presented with their show list for the year. Amongst that two of the major Studios showed off footage from Superman Returns and X-Men 3, and some kindly Internet people are letting us mere public see it. Thank the lord for technology.

The footage is very rough and not exactly high resolution, but there's some behind the scenes stuff and actual clips. Thanks to dTheatre for pointing to the Superman Returns footage and the X-Men 3 footage.