First things first....
1) Legalize drug use... tax the living hell out of the drugs. If someone makes the choice to use drugs, then they are responsible for their actions while under the influence, the same as with alcohol. No using the defense "well, i am an addict and thus should get rehab rather than prison". But no more putting people in jail simply for smoking pot. If they are not hurting anyone, go ahead.... your choice... but I am not paying for your rehab nor will I show you mercy if you hurt someone while under the influence.
2) Prisoners should work. It will teach them work skills that they can use upon release. Education should also be mandatory. Something like 2 hours of education a day, 6-8 hours of work, the other 14-16 they can use to eat, sleep, reflect etc...
3) As for "slave labor" comment... enough with the bullshit. It costs the taxpayers what... about $40k per year?? to house a prisoner. THAT is your compensation if you are a prisoner. You are repaying society for the money they are spending to rehab your ass.