David Coombes, Platform Research Manager for SCEA, gives a high level introduction to the general design and idea behind the architecture for the PlayStation 3. Covered in this session was general Cell architecture including the SPE, SPU, MFC, and DMA. Also explained were general technical demonstrations including a ray casting terrain engine and Alias cloth technology.
Lots of slides: http://www.gaming-age.com/cgi-bin/specials/page2.pl?spec=gdc_2006&pagenum=7