Questions
1) Who wrote the memo
The memo was written by a staffer at the instruction of Jay Rockefeller. Rockefeller has said so. It is not clear whether the memo was ever actually passed around to other Democrats. I think that's beside the point.
3) To whom did they leak the memo
The memo was originally leaked to Sean Hannity, the talk show host.
2) Who leaked memo
Sean isn't saying, but he considers the source reliable, and says it isn't someone you'd expect it to be.
This is as much or as little as we had on Rumsfeld's memo, and yet that became front-page news for days.