Martin has joined League One strugglers Millwall for an initial fee of £50,000, which could rise to £100,000 depending on appearances.
The 22-year-old signed for Palace in the summer of 2007 from non-league Dartford, and went on to make just 15 first team appearances for the Eagles.
Green, who was one of former manager Peter Taylor's first signing, came to Selhurst Park from Hull in the summer of 2006.
He played 27 times for Palace, scoring four goals. Sheringham, son of former England striker Teddy, was signed after he was let go by Ipswich. The 19-year-old did not make a first-team appearance for the Eagles.