General Movie Reference Sites

Internet Movie Database -- the place to go for the details: cast and crew lists, filming locations, quotes, bios, etc.

Hollywood.com -- I use their movie showtimes feature -- it's usually more reliable than the Washington Post's website (except for the time they confused Under the Sand with Under the Sun).
 

Movie Review Sites
If you want a second opinion...

Rotten Tomatoes -- it compiles a wide range of critics (the legit ones are in a sidebar) and rates a movie as "fresh" or "rotten," depending on the percentage of reviews that are positive.  The first place I go when I'm trying to decide whether or not to see one of my free movie previews.

Check the Grid -- though the rating system is simplistic, you can set up a grid of your favorite critics and see at a glance whether they give a movie a red light, yellow, or green.  You can add "buddies," too -- my buddy name is, of course, "megansmovies."

Mr. Cranky -- for an even crankier take on movies than mine.

Oh the Humanity -- funny reviews of "the worst films ever witnessed by mortal eyes."  Rates movie on "badness," "parody value," and "sex," and lets you know if there's a naked dancing girl during the opening credits (more common than you might think).  If you don't know where to start, click on "Random Movie," and you might discover a buried gem like The Terror of Tiny Town.

Stomp Tokyo -- another bad-movie review site.  A little more serious and fan-boyish than Oh the Humanity -- meaning their reviews are much longer and more detailed.

The High Sign -- if you like my writing but disagree with my assessments, you'll like this site.  She writes much like I do but diametrically disagrees with me on just about every movie.  Fun to read, though.
 

Information on Unreleased Movies

Release calendar -- SplicedOnline keeps a good calendar of release dates for upcoming movies and even notes "select cities" and "wide release" dates.  The site also has reviews, but I haven't spent much time exploring those.

Upcoming Movies -- good info on movies in production.  It notes rumors, title changes, filming locations, and other tidbits.  It also has a release calendar, but it's not as user-friendly as SplicedOnline's.
 

Movie Magazines

Entertainment Weekly -- pretty much everything that's in the magazine, plus occasional contests to win free movie passes.  Unfortunately, now for subscribers (and, I think, AOL members) only.

Premiere -- takes a while to get updated sometimes, but has a good archive of the magazine's stories.

Where to get hard-to-find films

I can't vouch for any of these services, but I thought people might be interested in them.  They rent and/or sell foreign, independent, and other hard-to-get films.

http://www.olivefilms.com/
http://www.nicheflix.com/
http://www.filmmovement.com/
http://www.specialtydvd.com/

Pop Culture

Pop Candy -- USA Today's pop culture blog.  I know -- USA Today?  But it's pretty good.

Mexican Movie Gallery -- wonderful collection of old Mexican movie posters.

Pop Cult Magazine -- "pop culture" being defined here largely as the 1950s, but they venture into present times mainly to be snarky.  Best is their "bottom 5" list (e.g., "Crappy movies HBO won't stop repeating")

James Lileks -- the Gallery of Regrettable Food, classic motels, the Institute of Official Cheer... collections of kitschy cultural detritus.

Archie McPhee -- purveyors of magically crappy and useless stuff.  Plus, free gift with every order!  (It often turns out to be some kind of rubber animal -- snake, cockroach, lizard...)

Inconspicuous Consumption -- Paul Lukas examines consumer products we generally overlook.  The book of the same name is hilarious.

Stella Marrs and Anne Taintor -- these two women create hilarious postcards and other items

The World's Largest Collection of the World's Smallest Versions of the World's Largest Things Traveling Roadside Attraction and Museum -- just go see it