HyperConomy is the all in one economy plugin.  It can run using its integrated economy plugin, or connect to an external Vault based economy plugin.  HyperConomy supports chest shops, Showcase style item displays, sign shops, information signs which can display price changes like a stock market, region based shops, global shops, and much more.  HyperConomy even includes an integrated web page which can display all of your item and enchantment prices.  For data storage, HyperConomy uses either MySQL or SQLite, allowing easy manipulation of data.  If you're running Tekkit, HyperConomy supports that as well; it should allow the addition of an unlimited number of custom items to the shop, allowing Tekkit servers to trade custom items.