There are actually several providers in this space.
CitySearch which has been renamed to CityGridMedia has a Publisher API where you can get their business listings, reviews, and other services: http://citygridmedia.com/publishers/
fwix's local API also provides basic geographic data along with local news: http://wireapi.pbworks.com/?geo_short=api
GeoAPI was recently purchased by twitter, and it provides a reverse geocoder, business listing information, and a bunch of other services: http://www.geoapi.com/
SimpleGEO also has a very compelling service offering with their mobile SDKs along with their API. You can search by radius, lat/lon, or by address: http://simplegeo.com/
Outside.in also has some great hyperlocal news information which is bundled up into a easy to use API: http://developers.outside.in/
Similar to CityGridMedia, MerchantCircle has an API that provides a listing of states, cities, zips, and categories. Along with business listing information, coupons, and reviews: http://api.merchantcircle.com/api/v1/docs
That's just the tip of the iceberg. There are other API services that specialize in more niche categories like Real Estate, Events, Hotels, etc.