I think it would be a really cool idea if you asked different CS professors if you could make a guest presentation one class to talk about functional programming languages. Some of them would probably be thrilled with the idea.
DO actually prep and come up with enough material to fill the time slot, though. One of my professors asked me to sub in for him when he was busy but the material was fairly basic (intro to SQL) and I was an idiot and didn't even bother finding out what they had just read.
I know my SQL reasonably well, but I had no idea what to actually say when confronted with an entire 50 minutes of dead time.
