The 2011 Abel prize in mathematics has to John Milnor for work on geometry, algebra and topology.
His discovery of exotic smooth spheres in 7 dimensions changed the landscape of mathematics. He went on to solve the problem in all dimensions. This was just a small part of his total contribution to mathematics described this morning at the prize announcement in Norway.
A talk on his work was delivered by Fields medal winner Timothy Gower, you should read his blog for a lot more detail.