I think you might have already covered this somewhere (or said why you wouldn't), but could "Effective sermon slides"/general presentation slides be a good topic for the show? Either way, you might like to watch: How NOT To Use Powerpoint By Comedian Don McMillan, which pretty much sums up the topic in a humorous way anyway.
More on PowerPoint
Having said that, I've just seen "PowerPoint Extreme Makeover", which is a longer, more detailed aid to this issue, which may suffice for many.