The silver and golden age of comic books 22,000 free read and downloadable.

The silver and golden age of comic books 22,000 free read and free download. For some of the sides you need to register first.
From Captain Marvel JR. to Batman you can read or download them at these two sites

http://comicbookplus.com/
http://en.wikipedia.org/wiki/Silver_Age_of_Comic_Books

It has become public domain so you can read or download them.
They can also be found at http://openculture.com