The Emilia Pinball project is an open source pinball simulator intended for linux machines by Henrik Enqvist. It has been reported to work on other unix variants also. Now a days there is also a win***s version, and a mac version might be on its way. Porting it to other systems should be easy as long as OpenGL and SDL (or Allegro) are working.
There is both an hardware accelerated version using SDL and OpenGL as well as an software version using Allegro available. The Allegro version is always a bit behind in development and has more bugs than the SDL/OpenGL version.