I would do a trade like this.
http://espn.go.com/nba/tradeMachine?tradeId=luol2ax The Wizards are in a playoff push mode. This should help (with Ariza's play not as strong as early in the season)
The Suns are in a playoff push and this helps without changing money on the book for next season.
Celtics role the die on Porter and cut Wallace's salary.
Basic
Boston: Out Green, Wallace and Humphries
in: Porter, Okafor, Seraphin and Temple
Wiz: out Ariza, Porter, Seraphin and Templ
in Green and Wallace
Suns: out Okafor
in: Ariza and Humphries. Would likely have to throw in a pick.