I highly recommend taking a look at Brenda Vogel's _Down for the count: a prison library handbook_ (Scarecrow, 1995) - it's still a great overview of the field + full of useful information.
The heydey of prison library scholarship really does seem to have been the late
'60s and early 70's (see "American Libraries" from that era for some really inspirational articles) but there is still research going on - a few interesting ones that turned up in a search of Library Literature:
Andersen, Lynn. "Expanding our work with prisoners", Progressive Librarian, no22 (Summer 2003) p. 62-4.
Geary, Mike. "Trends in prison library service", Bookmobiles and Outreach Services, v. 6 no1 (2003) p. 79-9.
Lehmann, Vibeke. "Planning and implementing prison libraries: strategies and resources", IFLA Journal, v. 29 no4 (2003) p. 301-7.
A few found on the web:
A Sept. 2004 article from ALA's journal on prisoners' reading habits:
A 2003 article from another ALA publication, "Three experts describe "how to be a successful prison librarian: 'preparation for a foreign land'":
And finally a 2003 profile of the Folsom prison library from the State Library of California's journal that gives some information about the
Re: job postings - there is no site that aggregates them, unfortunately (at least not that I know of). The CA Dept. of Corrections posts their openings here:
I hope this is helpful - while I didn't end up going into prison librarianship, I did a lot of research about it while getting my MLS and thinking about it, and have tried to keep up with the literature.