Some folks go into social work. There are numerous social aid or support programs that ex-convicts work in to both make a living and help others who are either incarcerated or on release. Some religious organizations operate prison ministries. Drug and substance abuse counseling is one field where there is a distinct possibility of obtaining employment if you have met the conditions of your release and have been in recovery (clean) since your release. Some of the most effective substance abuse counselors are ones who are recovering addicts who have been in the system-they know what their clients are going through and can be a positive role model. I should point out that many of the substance abuse counseling programs out there are privately funded or operated, so that might be one option to consider. Your best bet might be to talk to folks in that field and see what they have to say.
As for being a parole officer, I think it's safe to say that that would not happen. Having had any significant criminal history pretty much blocks you out to begin with. Then there's the budget cutting going on in local and state governments. My county laid off a significant number of probation/parole officers and even before the recession, those jobs were hard to come by in some regions. I grew up in Tennessee and literally, the only vacancies that came up there were when someone went got hired on by the feds, retired or died.

