There is the factory trac-loc which is a limited slip, but from what I have heard it is not the greatest.
A couple good options are
Detriot Tru-Trac: gear drive limited slip, much more effect than the factory one and no clutches to wear out or special oil needed. 350-400 dollars
Power-trax No-Slip: 100% lockup automatic locker. Some people complain of the noise and increase drive line slack but I love mine. Only about 350 dollars and can easily be installed yourself
ARB Air Locker: Selectable locker activated by air pressure. Very good piece of hardware, but not cheap. Expect to pay around 1000 dollars for the locker plus a small air compressor to activated it.
Unfortunately, Mopar doesnt offer any good factory options.
However, all 06 KJ due have traction control which some have said works quite well. So that may be enough for you. If not I would suggest looking into the Tru-Trac for mainly street use. Has better road manners than the No-Slip and you most likely don't need the 100% lock up unless you plan 4-wheeling. Plus I would assume with a good LSD like the Tru-Trac and the traction control you might have a nice system. If you are going to be doing alot of wheeling then you will most likely want one with 100% true lock-up like the Power-trax or ARB.
Also check out these posts
http://www.lostkjs.com/forum/phpBB2/viewtopic.php?t=7809
http://www.lostkjs.com/forum/phpBB2/viewtopic.php?t=7932
http://www.lostkjs.com/forum/phpBB2/viewtopic.php?t=7571
