England.
Ireland won the 2009 six nations championship
England last won the Five Nations in 1996. It became the Six Nations in 2000. See the related question below.
Scotland has never won the Six Nations although they won the last Five Nations in 1999.
Since the Six Nations Rugby Championship came into being in 2000, Wales have won it twice - in 2005 and 2008. Both times they won it with a 'Grand Slam', which means they were unbeaten in all five of their matches.
France won the Six Nations in 2010.
Italy have won a total of 8 games and a draw since enterying the six nations.
France have won 4 times under the banner of THE SIX NATIONS, but please remember that prior to this was the 5 Nations
Ireland
Yes, in 2013 Wales won the Six Nations for the 26th time.
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Ireland
2