There are many great resources online containing bibliographic information about comics. 

• Grand Comics Database: a great website that collects bibliographic information about comics publications as well as basic biographical information about creators. 
  • [DATASET] Grand Comics Database Project Dataset: Dataset associated with Comics.org. Hosted by the Library of Congress.
• The Comic Book Database: another great source for bibliographic information regarding publications and publishers.
• Coverbrowser.com: a collection of scanned covers for comics, pulp magazines, and fan content. Can be searched by title, artists, or even color. Companion site to vintageadbrowser.com.
• Digital Comics Museum: A fantastic collection of bibliographic information as well as full scans of Golden Age comic books.
• Mike's Amazing World: provides bibliographic data for a great number of historical comics publishers.