This comprehensive site has full cast and crew, technical details, and much much more.
The most comprehensive list of BTTF mistakes is at MovieMistakes.
A list of deleted scenes at Hill Valley 2015.
Kristen Sheley has compiled a list of changes that were made to the script, from first draft to shooting script here.
A comprehensive list of references to BTTF in other Movies, TV shows, Books, Comics, Music, Games and elsewhere. Go to Keith Gow's site here.
Why are all Doc's clocks exactly 25 minutes slow? See one theory here.
Did you buy the DVD box set before May 2003? Your discs may have a framing error. Go here to find out more.
Before message boards, there was Usenet! Keith Gow has written an article exploring the reactions of Usenet posters to the opening of BTTF. Go here to find out more.