He goes to Niger to find out if Saddam sought to buy yellowcake comes back and tells the CIA and the world he found no evidence of Saddam attempting to buy the uranium.

He calls Bush a liar in his NYT story, no Niger official says they had contact with Wilson and the Senate Intelligent Committee said after investigation that Wilson lied (made statements about authenticity of documents he never seen) and his work was so inclusive that claims of a Saddam and Niger deal was more credible.

Wilson lies and tells the press that vice-president Cheney sent him to Niger (probably in hopes the press wouldn't investigate further and expose his wife), but a memo Plame wrote proved otherwise and this wasn't the first time she recommended Wilson to the CIA.
A memo written by a Intelligent and Research analyst who took notes at the Wilson meeting to go to Niger was leaked and a few public people new Plame worked for the CIA prior to Wilson going to Niger.

Seems to me that Plame outed herself and not to concerned about being found out otherwise she would have not sent the memo recommending her husband and just stayed low, undercover.
It also seems to me that Wilson outed his wife with his outlandish media coverage. Did he really think the press wouldn't investigate him and find out about his wife after all the allegations he made?

There is also a article from the NYT (archive and you have to buy it to read it) from Nicholas Kristoff claiming Aldrich Ames, the highest paid spy outed Plame to the Russian's years ago and was moved back to DC to a desk job in fear of her life.

How many times can one be outed?

Joe Wilson is a bad man and was on a mission to discredit Bush and it failed, now the media is trying to finish it with Rove.

Let's see what facts develop. Who knows Cheney could have done it.