The Internet Movie Database is a favorite site of mine. Fast and comprehensive, you can find any film, actor, director, character and even television show in moments. Part of what makes it a great resource is the "external reviews" link on every film, taking you to reviews from some of the finest reviewers in the country. I recommend checking into the reviews of Kenneth Turan, at the Los Angeles Times, and Mick LaSalle, at the San Francisco Chronicle (with its little man, and his various moods, in place of a star ranking).
Find lots of films, new, old, foreign, what have you, at the Onondaga County Library. I talk about this in my first blog post.
Movie Trailers at Apple.com links you to a site with the latest trailers in various sizes and formats. Some trailers are posted quite far in advance of their release, so you can get an interesting heads-up about something that's not even on your radar yet. It's also a quick way to be exposed to diverse types of films. Get outside your comfort zone to see what else is out there.
Video Detective has new and old trailers as well as previews and isn't aimed solely at the Mac/Quicktime user.
Ain't It Cool is a site for all geeks and fanboys (and fangrrls). Science fiction, fantasy, horror, comedy, and other geektastic films are previewed and reviewed. Television shows and comic books also get a fair hearing. You get the inside stories via interviews with actors and directors; clips and stills from films still in production show up as well. It's an interactive site, where the readers engage in a no-holds-barred give-and-take (which is more informative and less hostile than you'd think).
Jonathan Rosenbaum is one of our great reviewers, a brilliant theoretician and historian of film who makes us ask hard questions about what we're seeing. He has several books containing reviews and essays on film. This site, featuring a different essay each week, contains archival links to brief reviews of hundreds of films.
Movie Scripts . . . is just what it sounds like. From my perusal of the site, it's clear that some of what you'll find is "shooting scripts"--what a director had in hand, rather than what ended up on screen. Some of these scripts are transcriptions from the actual films. Browse and enjoy.
The Internet Archive is a mini-library of multimedia original materials. The feature film link, which I provide, is just one facet of this online gem.