What Swivel and Many Eyes is for social data visualization (minus the commenting), GeoCommons [geocommons.com] could be for geographical mapping: allowing "non-technical professionals" to view and analyze geo-located data, without the traditional GIS overhead.
Relaunched a little while ago, the "Finder!" part of the service is designed to discover interesting publicly sourced datasets through browsing tags and categories, as well as upload, organize and share personally owned data. The "Maker!" part enables the creation of the according online maps, styled with shaded thematics, proportional symbols, graduated icons, points, lines and polygons without any required experience from the user. The so-called "Map Brewer" interface allows users to further classify and slice the data (e.g. quantile, equal interval, standard deviation, maximum breaks), and choose a base map layer (e.g. from Google Maps, Microsoft Virtual Earth, Yahoo Maps or Open Street Map).
I might be missing something obvious, but while I would love to browse through the maps already being made, I could not find any easy way to do so (except of hacking URLs). Also, is there any way to embed the maps in blogs?