For some time now I've been popping along to free film previews with ShowFilmFirst in the UK but I just found out they've now launched in the US too.
I can vouch it's definitely worth doing (especially getting in so soon after launch since there'll be far less competition for the limited seats)- I've probably seen about 15 films for free this year (weeks before release) through this website often with free food and booze and occiasionally even Q&As with the cast and crew.
Anyway, here's the URLs to sign up to the mailing list...