We have published a DC Comic Books Price Guide:

DC Comic Book Price Guide = Price List - NM Comic Books

So far we have researched the prices of close to 10,000 comic book issues. We will be adding a lot more as we research more prices. This price guide is specific to comics published by DC and to NM condition comic books, but expect soon to see also guides for other conditions, as well as other publishers such as Marvel.

Also check out the Marvel Comics Price Guide:

Marvel Comic Book Price Guide - Price List - NM Comic Books

and the Dark Horse Comics Price Guide:

Dark Horse Comic Book Price Guide - Price List - NM Comic Books

Happy collecting!