There was one I've been told was decent in New Haven a couple months ago (and I'm told Wizard bought it and it's going to be even bigger next year). And then there's the Webcomics Weekend thing that Topatoco and crew do in Massachusetts.
But generally when I'm looking for Cons I check out our calender here:
http://forum.webcomicscommunity.com/index.php/topic,123.0.htmlIt lists almost all the conventions. It's a pretty thorough.