V. I. Arnold has died of pancreatitis:

http://www.guardian.co.uk/science/2010/aug/19/v-i-arnold-obituary

I never met him, but I had the privilege of translating his book on ordinary differential equations into English for Springer-Verlag about a decade ago. More recently, I declined the chance to translate his autobiography, but instead reviewed it for the Mathematical Intelligencer. A mind like his does not come along just every decade, and he will be sorely missed. He was the last survivor of KAM. (Kolmogorov died in 1987, and Moser, the only one of the three I ever met in person---at Princeton in 1965, when he came to give a lecture---died some time during the 1990s.)

A monumental legacy is left behind him, I enjoyed studying his work.