I buy from good reputable dealers with a large stock. I like this family business called lotsofmotts on ebay. From their bio seems like they were in that Joplin Missouri tornado a couple years ago and then started their ebay store. They have a good selection of almost any us coins. All of the coins have a best offer option and they offer free shipping too.
I am just amazed that no one mentioned this guy-- http://www.ebay.com/sch/tazmicenterprises/m.html?_nkw=&_armrs=1&_from=&_ipg=&_trksid=p3686 one of the best sellers of moderns on ebay-- definitely an honorable business and I have purchased from them many times
Too many sellers to mention. If I've seen their name around and they have a 100% feedback and they have the coin I want, I'm most likely gonna take a chance and bid. With that said, most of my ebay purchases have been for tokens lately anyways, so maybe I don't qualify.