I know I am very late in this thread, but I have some thoughts I'd like to share.
For one, there are too many Christians consumed with end times conspiracy and trying to figure out the dates and the events of prophecy. They say this is the mark or that is the mark, or that this is the beast or that is the beast. The truth is that we won't truly know until it happens or God himself tells us. Most prophecy is very symbolic and isn't understood until after the fact.
Also, I am so dissapointed that many Christians are on the "Beast/Mark watch" so to speak, hoping they don't accidentally accept the mark and go to hell. I'd like to ask them to consider the power of Christ as savior if say inserting a chip in your skin can remove his work on your behalf. Ridiculous... Revelations is a warning to unbelievers, we as children of the almighty God have NOTHING to fear. We have no wrath or punishment to fear!
As far as who I think the beast is, I'd say Islam. But honestly, I am more concerned about the gospel than I am about who or what the beast is.