We try to limit slides to 50/hour, max. Naturally, I have colleagues who feel obliged to have some 100+ slides for a one hour lecture. I'm grinding my teeth thinking about this as I write!
My own lectures I try to keep around 1/slide minute, and a 30-40 maximum, because you need time to explain, and answer questions, and ask pimping questions too.
Probably between 200 and 300 a day depending on the lecturer. Same as everyone above, we had between 30-50 an hour for 4-5 hours. If you had micro in the afternoon.... Better add another 100 to that. lol. But realistically, the lecture notes were better, and you aren't going to go over every single slide. At least not at my school.