I'm not sure how many movie fans know this, but in addition to all those movies you can download illegally, and the movies you can pay to download from iTunes, you can also stream and download hundreds of movies absolutely free, with no fear or legal consequences. It's a little complicated as to how this happened, but these movies are considered to be in the "public domain," which basically means that their copyright has expired and was never renewed. This is very common for early movies made before 1923, and a little less common for movies after that, and nearly nonexistent for recent movies; copyrights received today extend -- apparently -- for 95 years.

Public domain is always in flux. Famously, Frank Capra's 'It's a Wonderful Life' (1946) was once in the public domain, which led to its being shown on television hundreds of times during the holiday season, on various different channels. Eventually someone discovered that the film's musical score was still under copyright, and now it has been scaled back to a once-a-year event showing.
Sites like Archive.org or Archive Classic Movies (no connection) offer large collections of these movies for streaming or for download. Other sites like Public Domain Torrents allow users to download movies in various formats, and are even ready to be burned to DVDs or for use on iPods. (The problem with this site is that it's not very popular and there are very few "seeders.") And Oldies.com sells public domain DVDs for about $5 each, with really nice-looking box art. Anyway, if you have your computer handy and some time to kill watching a movie, these are some of the gems you can watch, gratis.

1. 'Sherlock Jr.' (1924, Buster Keaton)
There are tons of silent classics available in the public domain, but the sad news is that most of them have been recorded at the wrong speed, so that the action is jerky and fast-moving (or, sometimes, too slow). They are also saddled with horrendous, headache-inducing musical scores ground out on an electric organ. Even if you can find great movies like Fritz Lang's 'Metropolis,' you're likely to see an edited version. However, I found one great silent era film on Archive.org: this great Buster Keaton comedy masterpiece. It even has the lively Club Foot Orchestra score that was recorded in the 1990s. It's a good-quality transfer, shown at the right speed, and very much worth seeing.

2. 'Night of the Living Dead' (1968, George A. Romero)
I bought my first 'Night of the Living Dead' public domain VHS videocassette in the 1980s, which seems too soon for a movie to have fallen out of copyright, but no matter. This is not only one of the great horror films, but also one of the great films, period. Like many films of the turbulent 1960s, it tapped into the unrest and anger of the period, but disguised it very well under a blanket of gore and creeping terror.

3. 'His Girl Friday' (1940, Howard Hawks)
Hawks' screwball comedy is the template for speed and snappy zingers; it's so zippy that even actors Cary Grant, Rosalind Russell and Ralph Bellamy seem to be amazed at what they're pulling off. The film slows a bit as it burrows deeper into its morally upright ending -- and I like it a bit less than Hawks' 'Bringing Up Baby' -- but it's still tons of fun.

4. 'Zero for Conduct' (1933, Jean Vigo)
I was amazed to see this on Archive.org, and in a fairly decent quality transfer, with good subtitles; it's not even available on DVD. It's widely regarded as one of the greatest films ever made, directed by a Frenchman who died at age 28, having completed only four films (three of them shorts). Running only 41 minutes, it's a free-form poetry depiction of a boys' boarding school with many stunning sequences, especially the slo-mo pillow fight. Francois Truffaut later paid tribute to this movie with his 'The 400 Blows.' (Watch the movie here.)

5. 'Superman' (1941, Dave Fleischer)
For me, there's no better adaptation of Superman -- be it a feature film, cartoon or TV show -- than the 17 cartoons made by Max and Dave Fleischer (and Famous Studios) from 1941 to 1943. Many of the Fleischer cartoons are in the public domain, including their amazing Betty Boop and Popeye cartoons, and their 1939 feature film 'Gulliver's Travels.' But these spectacular and colorful, simple and striking cartoons may have been the pinnacle of those innovative and largely forgotten animators. (Watch the movie here.)

6. 'Spider Baby' (1964, Jack Hill)
A bizarre comedy unlike anything else, 'Spider Baby' was revived and shown as a midnight cult film in the 1990s, but it seems to have disappeared again. It's one of my all time favorites for the oddball way it combines eroticism, horror, humor, and a heartbreaking sadness, mostly exhibited by Lon Chaney Jr., then at the end of his career and deep into alcoholism. He also sings the weird theme song! (Watch the movie here.)

7. 'Detour' (1945, Edgar G. Ulmer)
Edgar G. Ulmer's ultra-cheap, ultra-quick film noir is one of the nastiest, most lowdown of American films, and you can't take your eyes off of it. Tom Neal and Ann Savage star as the hitchhikers brought together by cruel fate. See also Ulmer's previous film, the terrific, atmospheric 'Bluebeard' (1944). (Watch the movie here.)

8. W.C. Fields Short Films (1930-1933)
W.C. Fields was once among Hollywood's top comedians, but despite his dry, cynical wit -- which would be perfect for today -- he seems to have been mostly forgotten. Some of his funniest short films are available on Archive.org, starting with 'The Golf Specialist' (1930); I love this one because of Fields' hilarious exchange with the little girl with the piggy bank. In 'The Dentist' (1932), Fields spends an excruciatingly funny amount of time trying to extract a troublesome tooth. And then 'The Fatal Glass of Beer' (1933) may be some kind of masterpiece with its weird, blank verse dialogue.

9. 'Scarlet Street' (1945, Fritz Lang)
With his predilection for paranoia and guilt, Lang was the purest of film noir filmmakers, and this, a remake of Jean Renoir's 'La Chienne' (1931) is one of his best efforts. Edward G. Robinson stars as a henpecked husband and amateur painter who falls for the wrong girl, the luscious Joan Bennett. (Watch the movie here.)

10. 'He Walked by Night' (1949, Anthony Mann)
Another great noir, this one was mostly directed -- without credit -- by Anthony Mann (Alfred Werker is credited). But the real reason to see this is John Alton's groundbreaking stark, harsh cinematography, which both heightened the realism of this film, and made it more artistic. The climactic chase through the sewers was copied a year later in 'The Third Man.' (Watch the movie here.)

11. 'The Stranger' (1946, Orson Welles)
Welles made this after his famous RKO contract blew up in his face, and he was groveling just a bit, trying to show Hollywood that he could make a "normal" movie. And so it's arguably the least interesting of Welles' directorial efforts, but it's also well above most other "normal" films. Robinson stars again, this time as a Nazi-hunter, combing small-town Connecticut for a notorious war criminal. Loretta Young and Welles also star, and John Huston worked on the screenplay. (Watch the movie here.)

12. 'Sita Sings the Blues' (2009, Nina Paley)
Paley's extraordinary animated feature ran into some copyright trouble surrounding its soundtrack of Annette Hanshaw songs, and so, due to some very complex legal language and/or loopholes, Paley has deliberately and purposely placed it in the public domain. It was one of the best movies of 2009, and now there's no reason not to watch it! (Watch the movie here.)

13. 'Beat the Devil' (1954, John Huston)
This is definitely one of the weirdest films ever made by a major director and star. Humphrey Bogart and Gina Lollobrigida star as a couple stranded in Italy while their steamboat undergoes repairs. Also stranded are a band of seedy-looking rogues (including Robert Morley and Peter Lorre). The plot has something to do with uranium. Jennifer Jones also stars, and Truman Capote co-wrote the screenplay. It flopped, Bogey hated it, but it has gone on to be something of a cult classic. (Watch the movie here.)

14. 'Carnival of Souls' (1962, Herk Harvey)
This moody horror film is sometimes cited as one of the worst movies ever made, but I love it. It was the only feature by Harvey, who otherwise made industrial films; it has very little dialogue and conjures up an amazingly creepy atmosphere as a pretty organ player (Candace Hilligoss) hits the road and keeps seeing a mysterious phantom. (Watch the movie here.)

15. 'Santa Claus Conquers the Martians' (1964, Nicholas Webster)
OK, this truly is one of the worst movies ever made, but being as it's Christmastime, I thought I'd include it. I genuinely like to watch it during the holidays (though many folks prefer the MST3K version, which is not in the public domain). The title says it all, as the Martians decide they need a Santa Claus on Mars and kidnap ours. Pia Zadora made her movie debut in it. You'll never forget the theme song, "Hooray for Santy Claus." (Watch the movie here.)