Javascript

OpenLayers

OpenLayers is a Javascript library that can display map tiles and markers loaded from any source in web browser. It provides an API for building rich web-based geographic applications.

Leaflet

This JavaScript library can be used to create mobile-friendly interactive maps. It does not provide data to map, but can be used to map spatial data in GeoJSON format, or display tiles from other sources such as MapBox.

timemap

Timemap.js is a Javascript library that helps you to produce online maps (such as Google, OpenLayers, and Bing) along with a SIMILE timeline. You can load one or more datasets (in JSON, KML, or GeoRSS) onto both a map and a timeline simultaneously. By default, only items in the visible range of the timeline are displayed on the map.

Mapstraction

Mapstraction is a Javascript library. It provides developers with a single interface for a wide variety of Javascript map APIs including Leaflet, Google, Bing, OpenLayers and ESRI's ArcGIS.
A key benefit is that once a developer has loaded Mapstraction, s/he can to switch from one map API to another quickly and easily - often only needing to change a few lines of code.
Mapstraction displays points, lines, polygons and markers on the maps, and also allows developers to add base maps and overlays.