Den of Geek reports that Sylvester McCoy, who played the 7th incarnation of the Doctor in the original run of Doctor Who, is slated to play wizard Radagast The Brown in the upcoming Peter Jackson film version of The Hobbit. McCoy was a contender for the role of Bilbo in the LotR movies.
Radagast is a minor character in Tolkien's novels, and he doesn't appear directly in the original version of The Hobbit. It will be interesting to see how Jackson plans to adapt him; the little bit of him we see in the novels hints at an earthy sort of wizard, more interested in hanging out with the beasts and trees of the forest than messing about with all this war stuff.