I've learned so much in such a short time by watching this documentary. It talks about the current breakthroughs in research about the different stages of sleep, some of the different hypotheses (from long ago, culturally, and scientifically), and even a database that is used to find patterns about what we dream about throughout our lives. This goes beyond Freud in that it begins to see the neuroscience of dreams. It is even now possible to see what we dream about (sort of) in non-REM and REM cycles. The two cycles actually serve very different purposes and inhibit different emotional responses for humans during waking time.
I highly recommend it. You will be inspired to start tracking and getting better at remembering your own dreams.