PARs are rapidly disappearing, as they're tough to maintain and there aren't many controllers to maintain currency. If I'm not mistaken, there are no more FAA facilities that provide PAR capability. Many still have ASR approaches available, but most PARs are going by the wayside at USAF bases due to cost. Luke AFB shut theirs down recently, and Nellis AFB stopped servicing theirs due to the inability to maintain controller currency. The Navy and Army still have many PAR facilities, mainly because USN aircraft ILS systems aren't compatible with civilian ILS systems, hence most USN aircraft are TACAN-only, with PAR as the only precision approach they can fly.
Also, the term GCA refers simply to the facility or as a generic term for a radar approach. One can't request a GCA approach without specifying whether it be an ASR or PAR, unless the field has only one or the other.
Here's my write up on GCA approach review that BobDuck referred to:
http://www.jetcareers.com/forums/showthread.php?t=4099