Shane Carruth's Primer is probably the great science fiction movie of the 21st century so far, and I believe it's the one of the most important films in the modern Golden Age of Indie SciFi. I love Primer. I have never felt entirely confused by Primer - I sort of always felt like I mostly 'got it' - until I looked at this incredibly detailed timeline from Unreality Magazine. Positing nine different time streams, and detailing where each one converges from the others, this chart kind of makes my head spin.
On the off chance you haven't seen Primer, now's a pretty good time to get on it. Don't blow your brain out by looking at this chart, though. Save that for after the film!
Click the image to see it large.