So I've been following where 2.0 via twitter and the videos published and feeling like I missed the party :(
Google Earth for NeoGeographers: Frank gave a good summary of what is possible with Google Earth from reading his PPT presentation.
Community GIS for New Orleans: Denice Ross and James Fee gave a good talk on using GIS and web GIS to provide New Orleans with spatial information. What I particularly liked about this was that they mentioned that they did user testing (details). I tend to advocate a less sophisticated testing regime than they describe, I think you can identify most of the problems with your web site without needing to work on users actual machines but it was a good write up.
It was also interesting to hear that James Fee did a good job of assessing technology needs rather than ploughing in and telling the clients what technology they should use.
4D Maps: Brandon Martin-Anderson talked about representing 4 dimensions on a map. There was some interesting stuff in there but I felt he missed out discussing the many examples of time in GEarth and also Hans Rosling's wonderful visualisation tools.