Google today drive techology like in the past many research center or university campus. Is like a worlwide computer science faculty that involve many developers in a way that is common in research center.
Thanks to this idea that drive their business today we can use a lot of feature available on their site with public API, and many Google Techology User Group are born in the world to follow this new trend in development (is web 3.0 ???).
Regarding their techs, I used a lot GWT for business and now I'm experimenting (now it's almost a year) Google App Engine's feature and potentiality.
Here you can find some (not so much indeed) articles I wrote during my experiment and work with them.