In my room:
A 5-disc changer, a burner, a PS2, and 2 drives on my PC, and a player hooked up to my capture device
Other rooms:
A DVD player in the family room, 2 DVD players downstairs, 2 computers with 2 drives each, a laptop, and an old DVD player that's not hooked up to anything
total: 15, 19 if you count all 5 discs in the 5-disc player