Mike’s Amazing World of Comics.
A web site where you can use a control panel thingy to enter your chosen month and year and get  thumbnail images of all comics that made their first appearance  on the newstands of America that month. Clicking on an image gives a larger image, publishing and creator details, plus the opportunity to view earlier and later issues of the title.
http://www.dcindexes.com/timemachine/index.php

Health Warning. This site has the capacity to consume great gobbets of  time without warning or awareness. Use with discretion.