(Background - a previous answer to this question--not sure how to link it--tells us City of Chicago publishes building violations.)
We've developed a free mobile app (Vancouver RentalDog, currently in iTunes) that allows people to identify licensed rental buildings in Vancouver, which have outstanding bylaw infractions. Our data is pulled from City of Vancouver and hosted on our server for access by mobile clients.
Any suggestions for contacts in other cities that have similar datasets? We're more than willing to work with IT staff to put their data into Open.