And there I thought I'd figured it out... Wired have a brilliant Top 10 list – 10 Best Head-Scratching Stories, Explained – which explains, in two lines, the crazy plots of some crazy books/movies/etc. 2001: A Space Odyssey I can accept, and Mulholland Drive I figured out myself. But I'm unconvinced about Blade Runner.
There's also a link in the Comments section, which is worth checking out: Uncomfortable Plot Summaries.