Not meaning to take away from the venerable Netflix thread with a similar title, I happen to be a subscriber to Amazon Prime (not Netflix, although I've heard nothing but positives about that service). I climbed on board with Prime after reading yet another "heads-up" post on e-r.org last year about a one-day deal on Prime for $72/year. I'm due to renew at the standard rate (I think $99/year) shortly and will keep it as I think it's worth it. I had very little interest when it was only an expedited delivery thing, but now I'm a steady consumer of movies and music (Beatles!). So I'm starting a parallel thread (but not a "less filling, tastes great" comparison) for Prime ideas.
Anyway, I'm currently watching a series of Ken Burns-associated documentaries, some of which I've seen and liked already, but some I've never seen. I'm now nearing the end of The West, which is billed as Burns but directed by Stephen Ives in a similar style. Being mainly an east-of-the-Mississippi kind of guy, there's a lot to learn for me and it's very enjoyable. The kind of thing you look forward to the next installment.
