NEW YORK (Reuters) - Pink Floyd's seminal stoner album "Dark Side of the Moon" is turning 40 on Sunday, and the band's website has developed an interactive feature whereby fans can help turn a specially designed moon on the site dark. Starting after midnight Sunday in England (8:01 p.m. EDT on Saturday), fans are invited to play back the classic album on PinkFloyd.com, then tweet their memories, photos or other thoughts and comments using #DarkSide40. The collective tweets will darken a side of the moon on the website, EMI Music said on Wednesday. ...