Take a look at iConomy 7 http://mirror.nexua.org/iConomy/7.0/iConomy.jar or BOSEconomy http://mirror.nexua.org/iConomy/7.0/iConomy.jar at least take one, which supports Vault: http://dev.bukkit.org/server-mods/vault/pages/using-vault/
http://dev.bukkit.org/server-mods/iconomy-continued/ ICONOMY IS BACK EDIT by Moderator: merged posts, please use the edit button instead of double posting.
I've seen Sleaker recommend CraftConomy as a good economy plugin. I'm going to guess that it's pretty decent.
iConomy and ChestShop. iConomy still works (for me at least)... As I say: Code: not updated != outdated
I used to use iconomy but it is always outdated and essentials economy is a lot easier and updated a lot more