The rules are simple:
1) The name on the sign must be "[Locality] House of Pizza," in that order, with no exceptions. Any sort of name of a nearby neighborhood or landmark qualifies as a locality.
2) The photo must be taken by me. Feel free to suggest houses for me to visit, but don't bother sending me photos of HoP that I didn't personally visit and photograph.
Oh, and I suppose I'm limiting it to Massachusetts, though if I happened to spot one somewhere else, I probably wouldn't be above shooting and posting it.
So far I've been told to visit the Millis House of Pizza and the Milford House of Pizza. I also seem to have deleted my picture of Andrew Square House of Pizza, so I need to take that one again.
I should mention that I've never eaten at a HoP, and I'm not sure I plan to. Most of my informants who've clued me in to the existence of a HoP in their neighborhood have also mentioned that the place was terrible. Just adds to the intrigue, as far as I'm concerned.