You often hear people — especially non-hacker types — complain that money spent on space travel would be better off spent here on Earth. Of course that ignores one big factor, that space programs have resulted in a host of spin off technologies, many of which you use every day. JPL has an infographic that covers twenty things we wouldn’t have without space travel, and while it could be said that some of these things might have been invented anyway it would doubtless have taken much longer without the necessity and the income from space programs. If you want more detail, Tech Briefs has an interesting interview on the subject of what tech spun off the Apollo program.
Some of the inventions are pretty obvious, and others are more refinements of things that already existed. We all knew NASA pioneered freeze drying for food, for instance. However, some of them are pretty surprising. For example, according to the infographic, NASA asking Black and Decker to develop a moon sample collector led to the Dust Buster.