I just posted on the "Sermons" page of the ECLEA website the sermon I preached yesterday on Rev 6:1-17 entitled "God and Evil." It deals with the important issue the world faces and we face as individuals, namely, the existence of radical evil in the world and God's relationship with it.
Many people cite the presence of such evil as a reason why they don't believe in the God of the Bible, but such an objection is not valid. Indeed, paradoxically, the recognition that there is universal and objective evil itself is evidence that God does exist and that he is good.
The sermon (both audio and PDF) is available at: http://www.eclea.net/sermons.html#revelation.