Although it is open to criticism at times, Wikipaedia has an article that lists POW Camps by number with their location.
http://en.wikipedia.org/wiki/List_of..._Camps_in_WWII
There is also:-
http://www.wartimememories.co.uk/pow/pow.html
The second one might be of more use as it lists Italian camps as well.
What was the camp number, if you can remember?
Paul.