Matthew 5:29-30
At first it could sound very much like he is referring to masturbation, but read it again. It says "If your right hand offend thee (KJV)", or "If your right hand causes you to sin(NKJV)" It doesn't specify what the sin is. It says "if", so "if" masturbating isn't considered a sin by itself, your right hand would not cause you to sin while doing it. So, it still does not condemn the actual act of masturbating. It would if it referred to masturbating while lusting after a woman.
Since the context of 5:27-30 is committing adultery in the heart, it would appear that he means actually using your hand to commit adultery or some other act of sin. Something like, grabbing a woman in a lustful way, or how about "sexual harrassment"?