OpenLayers is a a module for the open-source CMS Drupal that allows map mash-ups.
OpenLayers is an open-source alternative to Google and Bing Maps featuring standalone and interactive maps that can be embedded onto any web page.
From their homepage:
Tiled Layers: Pull tiles from OSM, Bing, MapBox, Stamen, and any other XYZ source you can find. OGC mapping services and untiled layers also supported.
Vector Layers: Render vector data from GeoJSON, TopoJSON, KML, GML, Mapbox vector tiles, and other formats.
Cutting Edge, Fast & Mobile Ready: Leverages Canvas 2D, WebGL, and all the latest greatness from HTML5. Mobile support out of the box. Build lightweight custom profiles with just the components you need.
Easy to Customize and Extend: Style your map controls with straight-forward CSS. Hook into different levels of the API or use 3rd party libraries to customize and extend functionality.
For more information and tutorials regarding OpenLayers, refer to Antonio Santiago’s presentation. From Slide #63, here are some examples of OpenLayers maps:
Web Feature Service (WFS)
Keyhole Markup Language (KML)
OpenLayers is open-source and its source code is available on Github.