Plugin to put Author’s Name at bottom of every post?

Hey,
I’m admin-ing a multi-blogger blog called the TOC, and we want to have the author’s name put at the bottom of their posts, automatically, so it would say “By Dodge Billingsley” or “By Grayden Ridd”, etc. I’m actually not sure if this even requires a plugin, in which case I’d much appreciate a howto or something to let me know how I can accomplish this. Thanks a lot!