I had a Machine Learning class last semester and one thing that I found really useful which isn't really done in any of my other classes was that the lectures were recorded and uploaded to YouTube. This allowed me to look at the given slides and essentially "relive" the entire lecture at my own pace, since there were parts that I'd understood quite well the first time I heard it, but other complex parts needed a few pausing and rewind to better understand what was being taught.
