Glider was this really nice game where you had to fly a paper plane through houses, making sure you got as far as you could by using the airflows from vents, fans and the like, while avoiding bad things, like paper shredders. I have fond memories of playing this on a black and white mac. Anyway, Glider PRO is free these days, and available for Mac OS9 and OSX, and the older Glider 4.0 is available for Mac OS6 & 7, and Windows. You can download it all here.

And there is an online version called Glider web, for all us non-mac people.