In or out of jail/prison? And the state makes a big difference.
Many states use inmates in jail/prison for armed road crews formerly known as chain gangs. These are inmates that require guards and return daily to jail/prison. Sometimes they can be used for projects requiring large numbers of bodies. Right at the moment, several states are using armed crews for sand bagging (you'll see the guard on the edge of the shot). These groups do not normally have any contact with the rest of the world. (See how many guns point your way when you go over to offer them some water.)
Some states have programs at their jails/prisons for such things as dog and horse training, farm stand, crafts, et cetera. In this case, most of the inmates do not have contact with the public, but a few might.
Inmates in their final transition from prison will be allowed to work without guards and may not have to report to the prison/halfway house on a daily basis if the program has a live-in potential. Some inmates will do community service.
Criminal defendants can have a community service component as part of their sentence. Usually these are done outside the Department of Corrections and the defendant has to arrange it themselves. This can include lectures.
What are you trying to do? Give me what you're trying to do and I can probably figure out how to get it done. God knows I've got some clients sentenced to some creative community service projects instead of jail.
Best of luck,
Jim Clark-Dawe