Ain't no Sunshine was a great one, but I think his most famous song was probably Just the Two of Us, which was on Grover Washington, Jr.'s Winelight LP.
update September 19, 2002
Bill Withers was born on the 4th of july in Slab Folk, West Virginia in 1938. His father died while he was young, and he grew up poor. He joined the navy as a young man, and pursued a singing career after a nine year term in that institution. He worked for Boeing making toilet seats and recorded demos at night.

After being discovered by a record company executive, he recorded his first album "Just as I Am. This album was produced by Booker T. Jones, leader of Booker T. and the MGs, the house band for Stax records out of Memphis in the sixties. It was this album that included the classic "Ain't no Sunshine". Among his hits are "Use Me", "Lean on Me", "Lovely Day", and "Just the Two of Us" with Grover Washington, Jr.