Is Black Stuff Coming From A/C?

Answer:
The black stuff you say is coming from your A/C is probably not from that but if you are burning a lot of candles in the house the blower for the furnace will circulate the soot from the candles and can cause "black stuff" to end up on everything in the house.
You also might want to try to get your ducts cleaned if they have a lot of dust and dirt in them then having them cleaned will reduce the amount of dirt circulated through the house.