Nashville, Robert Altman, 1975
Eric Idle's Personal Best (Not really a movie, per se, but a selection of Monty Python sketches)
About Schmidt, Alexander Payne, 2002
Wild Strawberries, Ingmar Bergman, 1957
I also caught about a minute of Andy Warhol's Empire (1964), which is currently being screened on a loop (well, a two hour segment of it) at MoMA. I pretty much got the gist of it though—actually watching the whole eight hours might only make sense if you want to be able to say you've seen it. Or maybe if you've lost a bet. Now that I think about it, it might be interesting to see while fast forwarding through it (at the fastest speed possible), illustrating the passage of time and the activity (or lack of it) occurring, but at a much more watchable rate.