Free, Public Domain Golden Age Comics Online
The Digital Comic Museum is a website that is collecting public domain comic books from the Golden Age of Comics, which is generally thought to be between the 1930s and 1950s, and is making them available for the low, low price of free.
The site is fairly organized, listing each publisher in alphabetical order, as well as providing popularity categories, such as Most Downloaded and Top Rated. Users are required to make an account before they can access the free comics archive, but it’s no worse than signing up for any other kind of internet forum.
The comics uploaded to the archive are in the standard digital comics format and can be best viewed with sequential image viewers, such as CDisplay (the original, no longer supported version) or CDisplayEx (a newer version with newer features, though reportedly buggier) for Windows, or Comical for OS X.