The GDC website doesn't have any videos of the sessions as of yet, but PowerPoint presentations are available for free and for $7.95 you can download the audio recordings from GDCRadio.
Here are the presenations and recordings that I found by the Maxis producer Caryl Shaw, and senior development director of Maxis Eric Todd. I also found the audio recording of session by Chaim Gingold, an associate game designer of Maxis, and Chris Hecker, a technology fellow of Maxis.
Building Community Around Pollinated Content in Spore
60-minute lecture by Caryl Shaw.
Overview: This session explores how user-created content in
other Maxis products like SIMCITY and THE SIMS 2 created a different
kind of online community and how those lessons are being applied in the
Pollinated Content System in SPORE. Specifically, the talk looks at how
to tailor the system to appeal to both users who specialize in creating
content and users who are more likely to download someone else's
creations.
Spore: Preproduction Through Prototyping
60-minute lecture by Eric Todd.
Overview: This session
explains how prototyping can be the heart of a virtuous cycle during
preproduction. The cycle is illustrated with concrete examples and
numerous prototypes from Spore's preproduction phase. Potential
pitfalls are highlighted.
Advanced Prototyping
60-minute lecture by Chaim Gingold and Chris Hecker, intro: Will Wright
Overview: Creating effective
prototypes of game designs, user interfaces, and technologies requires
a unique set of skills and knowledge, somewhat distinct from the skills
used in making a game. This lecture discusses creating these various
types of prototypes from an advanced and in-depth perspective. The talk
goes through a number of important questions and topics that should be
addressed before, during, and after the prototype is created, including
metrics for judging the effectiveness of prototypes, how to decide the
focus of a prototype, how to design, start, and build the prototype,
both from a content and a code standpoint, and how to iterate the
prototype via testing and integrating feedback. Various approaches to
these issues are compared and contrasted, with the end goal of teaching
attendees how to create successful and high quality prototypes.