With all this talk of actual theaters I don't know if "six people watching a 42" plasma in a basement" constitutes a watch party, but I recently learned that neither my friend's girlfriend nor his roommate have ever seen any Star Wars movie, and since we agree this cannot stand, I'm planning on hosting a few folks for a Harmy marathon in the near future. I'm sure I'll also have people over when your Star Wars is available, maybe do it as a double feature with the Grindhouse ESB.
As far as legitimate theaters go, I'm probably going to bite the SE bullet and go to the AMC marathon unless any of the indie theaters around here end up hosting their own events. Luckily, there's enough underground stuff in Boston that that isn't a completely crazy thing to hope for.