I will have to contradict Hepcat here and say DON'T try selling it at comic cons, and go for ebay or craigslist instead.

Basically at NY Comic Con 2 weeks ago, I felt I got...pretty badly ripped off and had a very frustrating experience trying to sell my box-and-a-half of comics. Walking from vendor to vendor and being rejected until I finally sold them to someone who gave me a really really low price. I would have rather kept the comics instead of the $25 he paid for them.

Whereas on ebay I don't make a killing exactly, but I get a lot more than that. I sold some of Grant Morrison's Batman run for like $11. Not amazing, but considering I sold so many more comics for only $25, I feel like I would have had better luck on ebay in the long run. The problem is comic vendors at comic cons are too knowledgeable and wary about being ripped off and will either reject you or haggle you to death. I prefer just going directly to my fellow comic book readers.