There's Final Fantasy: The Spirits Within. It's a Final Fantasy title, obviously, but it really has nothing to do with the series in terms of plot comprehensiveness. It's its own story, really. I dunno if you'd consider it anime...whatever. Other than that, I'm not really well-read ("watched," in this instance) when it comes to anime movies outside of Miyazaki's...
As for Akira, I, personally, wasn't too fond of it, but it's widely regarded as a classic so I would definitely reccommend watching it for knowledge's sake, if nothing else.