Much depends on the type of work and on the contexts in which it is performed. I would argue that prison labor should be compensated in some way, perhaps financially. If work is used as punishment, it sends entirely the wrong message, and I'd suggest that the prison is losing sight of its primary mission, which is rehabilitation. Obviously, part of that mission should be providing inmates with skills they can use upon their release, and I also believe that more effort should be invested in providing education to prisoners.
I absolutely agree with prison labor and for most of the reasons named in the previous post. In most cases, prisoners are given extra time served for extra or hard labor, so it enables them to earn credit toward release. I also believe that prison life should not be an easy one; all prisoners should be required to work--both as repayment for their crime and for the skills they learn to use upon release.
For the most part, I do agree with prison labor. Prisoners should be taught a trade so they will have some skills when they leave prison. Hopefully these skills will help them become contributing members of society. On the same note, these prisoners should contribute to the society that they have wronged while they are serving their time. Of course, this labor should be undertaken in a humane way. I do not agree with working prisoners in unsafe or inhumane ways. Here in the US, prisoners are often put to work cleaning roads or making products within the prison walls.