On this page you can find the slides (.pptx), sample data (.Rdata), and code (.txt) from a workshop on mixed-effects modeling in R that we held at UCL on 18-20 May 2016. I try to be a slide minimalist, so I can't guarantee that the slides will make much sense on their own, but anyway they're here for posterity and just in case they're useful to anyone.
Sample datasets:
by Stephen Politzer-Ahles. Last modified on 2016-05-25.