Are there any APIs that will provide the hours of operation for a business at a particular location? Google Places, SimpleGeo, and Yelp don't seem to expose it. If not, is there some dataset that exists (again, i couldn't find one on data.gov or anything) that i could use to create such an API?
The feature request to the Google Places API mentioned by Mihai Danila has been since fulfilled.
Opening hours are now returned in Place Details results where available: https://developers.google.com/places/documentation/details#PlaceDetailsResults https://developers.google.com/places/documentation/details#PlaceDetailsResponses
Place Search results also now include a property that indicates if a business is currently open.