Even Google Map is free to use and have a large library and blogs to help. It’s good news for developer that there are more Maps Library available now to integrate in your application 🙂

Don’t worry to increase or learn new library of Maps, as each Map library have some unique feature, so match your requirement and integrate the Map that best suit to your requirements.

The Advanced functionality of these Maps are available on their website, I am also adding the URL of the Map API library.
Go through from these and increase your knowledge about the MAP.

1. Microsoft Bing
http://www.microsoft.com/maps/
Microsoft’s Bing Maps gives you a rich set of tools to help you create amazing map experience. Choose from our super fast AJAX Control 7.0, REST Services API.A unique feature of Bing maps is their ‘Bird’s eye’ view, which gives aerial views from several perspective angles.

2. Nokia (Yahoo Maps)
http://developer.here.com/
Nokia purchased Navteq (one of the major suppliers of map data) in 2007, and has been powering Yahoo maps since 2011.It provides APIs for mobile applications and web browsers.
JavaScript API, REST API, Mobile HTML5 Framework, Java API, Qt API is available & working fine for Nokia Maps.

3. MapQuest
http://developer.mapquest.com/
MapQuest is the company that lets you choose between using licensed maps or open maps. Even using licensed map data, it has free accounts with no limits on map views. However, it does limit you to 5K calls per day for routing (including for multiple destinations), geocoding, and search.

4. OpenLayers
http://openlayers.org/
OpenLayers makes it easy to put a dynamic map in any web page. It can display map tiles and markers loaded from any source that shows how flexible and powerful API designed to be used in advanced mapping applications.OpenLayers has been developed to further the use of geographic information of all kinds. OpenLayers is completely free, Open Source JavaScript. It is a mature API with lots of features, but it can be difficult to use in mobile applications since it was designed before they became popular.

5. Leaflet
http://leafletjs.com/
Leaflet is a modern and newest open-source JavaScript library for mobile-friendly interactive maps.
Many of the companies switching away from Google Maps use the Leaflet API. It was designed to work well with both desktop and mobile applications and is small and fast. Being newer, it is not as powerful as some of the other APIs, but what it lacks in features it makes up for in flexibility. It has a powerful object model that makes it easy to add features or customize existing features to your needs.

6. Modest Maps
http://modestmaps.com/
As its name implies, Modest Maps is a small, extensible, and free library for designers and developers who want to use interactive maps in their own projects. It provides a core set of features in a tight, clean package with plenty of hooks for additional functionality. There are lot of ports, including for Python, PHP, Processing, and Open Frameworks facilitate using Modest Maps in desktop (non-browser-based) applications, native mobile applications, and on servers.

7. Polymaps
http://polymaps.org/
The goal of Polymaps is to better support rich, large-scale data overlays on interactive maps by extending the tile metaphor to vector graphics.
Other APIs use image tiles to render maps, but they still need to display geographic information (such as markers and routes) by rendering it directly. Map data can be loaded using standard formats such as GeoJSON and rendered directly.

If you have gone through the documentations of these all, you have found that every Map API is unique in his way, so choose the best suits.
Anyway, if you think Google Map is more better then these all, go ahead with Google Map 🙂