I thought I'd go ahead and point this out. Andy Hamilton does a humorous documentary about Satan and how the idea has changed over time. The link has an embedded YouTube video that will probably end up being taken down sooner or later, so if you don't have access to BBC Four, you should probably watch while you can.
I'm only partway through as I type this, but it's looking fun so far. I'm curious just how much (or rather, how little) information about Satan is actually in the Bible. I pretty sure a huge bulk of the common perception will be linked to Dante's Inferno.