The presentations from the Where 2.0 conference always blow me away. I just been looking at some, and three in particular caught my attention. The first was Jack Dangermond's "Realizing spatial intelligence on the GeoWeb" The idea behind the talk was that geographic knowledge created in GIS environments is increasingly being made available to Web 2.0 users.
Other interesting talks with regard to building city models and understanding cities was Ludvig Emgård "World's Most Realistic 3D City Models?" and John Geraci's "DIY City: An Operating System for Cities."
GIS and Science blog