Billy Preston sadly died aged 59 earlier this week. He was of course famous for his work with the Beatles and Stones but it is solo material and session work with Sly Stone and Aretha that is closest to my heart.
If you don't have a copy of Billy's Bag do yourself a favour and get one double quick, Hammond craziness at it's best and dancefloor dynamite too boot. Most Exciting Organ Ever released in 65 and Wildest Organ in Town! from 66 are both cracking albums and well worth checking out. There's an excellent compilation of Billy's sixties material also called Billy's Bag that I can thoroughly recommend.
The BBC has an obituary on their site