At a glance:  MONKEY

Links:
  - Monkey Homepage
  - Screenshots
  - Winamp.com
  - Back to Geisswerks

A journey through a never-ending network of randomly-generated caves, with various shading and texturing options, and various very-cool 3D modes (for use with red/blue, red/green, or cyan/magenta glasses, as well as Chromatek colored glasses; use F6 and y/Y to tune the 3D settings.).