Ok so basically I am talking with someone about building a way for users to post locations to a map and have a pin over the location.
I know Google Maps can do this and probably has the best documentation/support. I was just wondering if/what other options there are. I have found Pushpin and Mappy but I really don't know much about either of them.
So what maps do you all work with/why?
Have a look at OpenStreeMaps. No licencing issues.
So to answer your question. I use the Google Maps API.
Why?
I think there are a whole lot of good reasons that make Google Maps an extremely valuable mapping solution for web developers. I realise I will probably sound like a hand waving evangelist, but here goes:
If you want to use a framework for building applications around maps in Java, you should have a look at http://www.geomajas.org/ which is an open source web mapping framework. This gives you both a mapping front end (using GWT), and powerful integration of different data sources. Amongst other options, you could use OpenStreetMaps for base data and integrate that with many other layers. And it is all pure java.