The Google Places API is now on general release and a Places Library has been added to the Google Maps API.
The new Places Library allows map developers to display venues in Google Places on a Google Map. The venues can be added either via a bounding box or within a radius of a centre point. The displayed venues can be refined by type (e.g. gym, food, zoo, art gallery etc) or by name (e.g. Starbucks).
The Places Library can also display details about the returned venues, including full address information and user ratings.
The Places Library for the Google Maps API doesn't seem to support check-ins. So if you want to give your users the ability to check-in at venues it looks like you will have to use the Google Places API itself with your Google Maps.
Via: Google Geo Developers Blog