Just posted the following list of local search api’s on SearchEngineLand. I am going to be maintaining the list here and will be updating it from time to time.
Alcatel Lucent Open API Service Tap into network data to pinpoint a user’s location via their mobile device, enable geotargeting of ads & offers and finding friends nearby.
CityGrid (CitySearch) 15M+ business profile listings. 3M+ user & editorial reviews. 500K+ local advertisters (in other words they will pay you to use this API!).
Earthmine 3D street level imagery to make your maps and local pages look really cool.
Foursquare Become the mayor of your own money-making application. Create strange new ways to check in at places at all over the globe.
GoWalla Like Foursquare’s but with a twist. I particularly like the LunchVote feature that helps you decided where to eat for lunch.
Hoovers Access 65 million company records and 85 million people records. That’s an insane amount of data. Includes historical financial performance, executive contact information and a lot of other stuff to make a sweet local business directory.
Outside.in Easily integrate hyperlocal news into your application.
Praized Create a real-time local recommendations service. This one is awesome.
TownMe Find and share local info. Gives a set of points of interest close to a lat/lon. These guys are creating an open platform for local.
Trulia Get geolocation data like lat/lon on neighborhoods, cities, counties, states and zip codes. Also provides a lot of real estate related data like the average price of a homes listed on Trulia.
Twitter/MixerLabs Do I really need to provide more info on this one?
Yahoo! Local Search for businesses near a specified location and return lat/lon and Yahoo! user ratings of the business.
Yelp API Retrieve business review & rating info, neighborhood name and pictures for a particular business or businesses in a particular geographic region or location.
WhitePages.com Allows you to add Whitepages’ people search to your site.
Zvents Restaurant and event venue listings, local events & performers. Zvents users and tags.
If you have any other great local-related APIs please add them to the comments below.