The 33-year-old former Reading and Stoke forward scored 12 goals in 37 appearances for the Blades last season after joining the club the previous summer, but has been released by new manager David Weir.
Midfielder Barry Robson is also heading out of Bramall Lane - he has agreed to join Aberdeen when his Blades deal expires - as are defender Lecsinel Jean-Francois, midfielder Matty Harriott and goalkeeper Danny Coyne.
Weir, installed as Danny Wilson's permanent replacement earlier this month, has handed new deals to defenders Danny Higginbotham and Aaron Barry, midfielder Callum McFadzean and striker Jordan Chappell.
Four other youngsters have been handed new contracts with Jordan Hodder, Terry Kennedy, Jahmal Smith and Elliott Whitehouse all looking to establish themselves in Weir's first-team plans next season.
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