I actually discovered that there was a third drummer between Pete and Ringo.  Forget his name right now, but he recorded one song with them, Please Please Me or Love Me Do.  There are two different versions out there, one with Ringo, and one with the other guy.  There is also a version of the rooftop concert stripped of Phil Spector's influence, Let It Be...Naked.  Gonna look it up later today.