Last I checked Google and Yahoo do NOT allow you to put their maps behind a login for a commercial application. Not sure about Microsoft. The only other option that I know of is OpenStreeMaps, which I assume is free. OpenStreetMaps says to use one of these third party APIs OpenLayers, Mapstraction, Staticmaps or CloudMade’s Web Maps Lite for their maps
did I miss anyone?
So my question to be more specific is: In terms of price, quality, performance and ease of implementation which one is best?”
Buying an license from google, yahoo or microsoft may be an option if that is possible. The concern with OpenStreeMaps is quality, performance and ease of implementation.
Note: We are only interested in JavaScript APIs.
I’d give a +1 on the Polymaps front as the guys from SimpleGeo and Stamen (with help from Mike Bostock) have done an excellent job with the library. It’s fast, easy to use and powerful.
Additionally, I think the following are worth checking out.
OpenLayers – Not as flashy, but very powerful and well supported by an active community. Mobile support a bit lacking at the moment (if that is important to you), but active development is going on to try and address this.
Tile5 – A reasonably new library focusing on HTML5 and mobile features, but introducing compatibility with IE7 and above. Disclaimer: I started the library and continue to work on Tile5, so I think it’s pretty good, but I also think these other libraries are also.
Leaflet – Just announced from mapping company Cloudmade (powered by OSM maps) this API offers similar compatibility to Tile5, and I have to say it is very well done.
The good news is that I believe you are spoiled for choice, it’s just a matter of deciding what is important to you and then making a selection on the library that best fits your requirements.