"Celebrate" from DJ Shadow's "Schoolhouse Funk Raw II" compilations. It's a cd with funk renditions of pop and rock songs performed by high school bands from the 70's, and "Celebrate" is the most outstanding song of the bunch, I can listen to it all day! There's a slight cheese factor to the singing style, but I think that's what made the song so groovy. Another good one is "25 or 6 to 4". You can listen to the high quality samples here (tracks 2 and 23).