If you have a large comic collection, or individual hard-to-find books, you can sell them at several sites online. You'll probably make more more money on ebay, but if you don't want to deal with the whole auction thing, here are some online stores that will buy comics from you:

 

ScottsComics.com - Buys old and new titles, everything from Batman to Pinky and the Brain

 

Fantasy-Comics.com - Buys Silver, Bronze, and Golden age Marvel (whatever that means :p ) and other classic titles

 

MyComicShop.com - Buys all pre-1980's comics and some 1980's and later. 100% of guide for 1961 and older

 

ComicsForCash.com - According to the site, they buy anything. Will also sell your collection for you on eBay, for a small percentage of the auction price

 

I don't know if any of these places will rip you off or not, so do your research before conducting business with them.