We have two great new showcases up the Cesium website.
smapshot, a project of the University of Applied Sciences and Arts in Western Switzerland, uses crowdsourcing to geolocate archived images, allowing users to see historical views in a geographical context:
http://cesiumjs.org/demos/Smapshot.html
AllisonHouse, a digitally focused weather data provider, displays forecast and real-time weather data on its 3D interactive viewer: