OpenStreetMap

OpenStreetMap's API is free and open, making it accessible to all developers.

It follows RESTful principles with OAuth2 authentication for editing capabilities. The API is powerful for map data retrieval and editing, supporting various programming languages through community libraries. However, it's designed for editing rather than read-only purposes, and the data structure can be complex for newcomers.

Rate limiting and usage policies must be carefully followed. It's ideal for developers needing open map data, but consider specialized map services for simpler use cases.