Getting into Google Maps is proving to be relatively painless. The Javascript API at least. V3 doesn't require an API key or anything like that either.

Start with the basics and go down the sidebar.
_ http://code.google.com/apis/maps/documentation/javascript/basics.html
_ http://code.google.com/apis/maps/documentation/javascript/overlays.html#KMLLayers

Fusion Tables is nice for working with others that are concerned with map content
_ http://code.google.com/apis/maps/documentation/javascript/overlays.html#FusionTables
_ http://code.google.com/apis/fusiontables/docs/developers_guide.html#Geo

Geocoding
_ http://code.google.com/apis/maps/documentation/javascript/services.html#Geocoding
_ http://code.google.com/apis/maps/documentation/geocoding/index.html

While going down the list of Fusion Tables features, heat mapping caught my attention, but I didn't want to rely on Fusion Tables to provide the data, because at the moment it requires it to be publicly accessible.
_ http://code.google.com/p/gheat/
_ http://www.google.com/search?q=google+maps+heatmap