Math circles this week have been noting the death of outstanding and influential mathematician/topologist (and Fields Medalist) William Thurston on Tuesday at age 65.
Terry Tao's obituary to him here:
A famous essay Thurston wrote entitled "On Proof and Progress In Mathematics" is available online here:
(or you can google it if you prefer it in pdf form)
ADDENDUM: just adding a couple more links (to Scientific American and the NY Times) from the many memorials to Thurston :