My husband thinks there is a movie from the 80's (NOT FLIGHT OF THE NAVIGATOR) where a kid builds a spaceship in his garage/driveway using everyday parts. I think he IS thinking of Fliht of the Navigator, does anyone know differently? We are dying here, we spend at least an hour of day discussing this...

This is a bit of a stretch, but the only other movie I can think of that it might be is Radio Flyer (1992). The boy in Radio Flyer is building a plane rather than a spaceship though. He's building it so that he can fly away from his abusive stepfather. Anyway you can check it out at the IMDB:

http://www.imdb.com/title/tt0105211/

I'm thinking "explorers" with young ethan hawk