A
DVD rental company operating exclusively online, NetFlix mails you the movies you choose with a postage-paid return mailer.
Their flagship program, Marquee, is an "all you can rent" salad bar of movies. They charge a monthly fee, and you get to have up to 2, 4, or 8 movies (depending on the fee you choose) checked out at any time. You can keep them for months at a time if you want, or you can rush them back and get new movies.
I've had some interesting customer service issues with them, but my case seems to have been an exception. Overall, it seems a decent opportunity to see lots of movies without having to worry about spending loads of money on separate rentals...