First the Google Earth, then comes plug-ins to have the Google Earth on your website followed by extensive kml and tour embeding options on your BROWSER. Yes, the 3D digital mapping is kicking off, very quickly starting from desktop application to your browser...the armchair cartographers and enthusiasts can be the virtual Columbus reaching every corners of the globe just by downloading some plug-ins!
Of course, it is not cheap to have spatial information in 3D from all over the world, so there is a very popular solution: crowd sourcing. Google has been doing it through the introduction of Sketch up, and now building maker (very powerful tool), where Microsoft has tried some options like Truespace and turned back to professional help from their own team in pursuit of the 3D cities. The competitions grow and so do the 3D virtual cities.
In an attempt to provide true (actual height plus some errors) 3D experience, a project called skape (not Skype) is another example of a struggle to attract more "users" in the virtual 3D world. Skape is getting Lidar data (with height information) in order to have true height of urban areas that will particularly benefit municipalities, environmental planners (at least they claim it) and of course, people like you and me!
Those are just the examples from the spatial world. Yes they were there before...but just arrived on your browser recently. More importantly, you will have the real 3D web browsing experience soon, Google, the giant, has recently (not that recently though) released O3D web api that allows you to create rich and interactive 3D applications in the browser. There you go!
