Geospatial Visualisation = Cartography or ? Well GIS has roots in computer visualisation and graphic design so where else but to start looking in these branches for new developments and here is what I found.
threejs threejs for 3d visualization in the browser
cesiumjs.org more cool 3d geospatial visualization on the web
dojo Combine OpenLayers map data with additional features such as geo-referenced Dojo graphics shapes or geo-referenced Dojo widgets on top of the background map.
Google Charts Google charts can produce maps using google maps api
Modestmaps modest Maps is a small, extensible, and free library for designers and developers who want to use interactive maps in their own projects
Kartograph Kartograph is a simple and lightweight framework for building interactive map applications without Google Maps or any other mapping service.
this list is by no means complete and I welcome anyone to help fill this out.
Great links to more visualisation goodness: