If you go back through history, abnormally high oil prices lead to slow economic growth. Oil prices then drop due to the slowing economic growth and also because the abnormally high price meant new means of extraction become economically viable. At the moment oil is dropping due to increased supply from shale gas and over time, the lower oil price should actually help economic growth. Now, economic growth is not really correlated with stock market growth (Just look at SA as an example of this) so this is really just FYI and not overly related to your question
Personally I think the rise in renewables, EG wind and solar will also put a dent in the oil price, and recycling will will also add to this. Was the Lehman Bros collapse a catalyst and those 140 USD odd a barrel days add to the momentum
So - a quick assessment here. The world consumes roughly 93m barrels of oil a day. At $100 a barrel - this is close to $10bn a day. Bring that figure down to $64 a barrel - we are injecting roughly $3bn a day into the global economy ($90bn a month). The real economy mind you - That is better than any QE program out there!