Christian Annyas is doing a great job collecting movie titles on his Movie Title Stills Collection. The movie titles are a wonderful time capsule of design aesthetics throughout the 20th (and early 21st) century, with each decade displaying its own characteristic look.
The site itself is really nicely designed, too, with a terrific movie-promotion feel to it. Christian links to two other movie title sites, and it's interesting to see the contrast. Steven Hill's Movie Title Screen Page has a welcome-to-1996 feel to it, with bits of content all over the page, mixed with ads in an incoherent pile. And Movie Title Screenshots has many more images (5700!), but in an page that feels like an undistinguished gamer's-forum warehouse.
In the deeper end of the pool, The Art of the Title Sequence doesn't just collect images, they provide the entire sequence, often with commentary, interviews with the creators, or preliminary work.
Lastly, we can't talk about movies and design without including Mark Simonson's Typecasting, about "the use (and misuse) of period typography in movies", an obsessively detailed look at the type that flies by on props, both accurate and inaccurate. Mark's been adding to the series as his snark moves him.