The OpenStreetMap library for Android supports the API functionalities that include overlays of markers and tracks. Java users might benefit from additional API uses such as reading and writing operations of the OpenStreetMap database.
Five years ago Paul Rademacher reverse engineered Google Maps to put Craigslist homes and rentals on a map on his site. The site essentially pre-launched the map mashup category, because there was no Google Maps API at the time. Now it is the prototypical example and still used by many to find their new homes. And, of course, Google Maps is now by far the most popular API to use.
In February of this year Radar Labs, Inc., a provider of location data infrastructure, announced the private beta release of several new APIs that handle geocoding, search, and distance. These APIs are now being moved into general availability and are receiving more affordable pricing.