PBOS (Pinball Operating System)
March 5th, 2009
Stumbled across this on RGP:
I have the code for my PBOS working to the point that I can coin up
1-4 players, and play a full game on the machine. Not to make it sound
too advanced, it does not do a lot, like score and multiball and most
of the sounds yet. But it has flippers, bumpers, slings, FIRE targets,
POWER targets, 1-6 targets, some sounds, and other stuff.
His website goes into some minor detail on the goals and progress. You can view that here: http://www.pbos.info
I don’t know about you but I sure hope he releases everything to the open source community. I’m a bit biased since I might be able to take it apply some/all of it to my machine. 
You see Dwight Sullivan’s blog, where he’s posting an interview of him from a Dutch magazine? The last two parts in particular might be interesting to homebrew folks.
Link?