Paul Williams (@ArchivistPaul) has mapped Alton (Hampshire) town centre in super level of detail for @openstreetmap -
see here - including 3D - see
F4map here.
Peter (@pbb72) has started doing similarly for Trondheim, Norway - see it on
F4map here.
F4map is a company (see also the
Wiki entry) that specialises in 3D mapping, using
OSM as its base. You can see some impressive demos above.
Unrelated to OSM, another project generating 3D imagery of buildings is
VarCity which is aiming to recreate cities in rich 3D from images harvested online. It’s kind of like the inverse of Google Street View: the photos aren’t illustrating the map, they’re the source of the map itself.