Centor Comics
Catalog of comics, complete sets and story arcs, ashcans, non-sports and sports cards, promotional posters, and vinyl record albums.
http://www.centormedia.com
Capital Comics
Golden Age to Modern Age back issues, many CGC graded.
http://www.capitalcomics.com
Blasto Toys
Retailer of comics, toys, graphic novels, Japanese imports, Gundam models.
http://www.blastotoys.com/
Comic Cavalcade
Exclusive and special edition comics and back issues.
http://www.comcav.com/
Comic Book Bin
Back issues for sale and comics reviews.
http://www.comicbookbin.com
Comic Art Community
Auctions for original comic art and related commissions, plus message board.
http://comicartcommunity.com/