I've been slowly working down the 2009 list in the order that they're listed here: http://www.singularityvolunteers.org/opportunities/transcription/videos
Doing them in popularity order might make more intuitive sense, but doing them sequentially might result in fewer collisions if multiple people are doing it simultaneously. See also my reply to lukeprog.
Edit: completed on 30-Jan-2012 (note deadline slip from 31-Dec-2011)
After some prompting I'm now going to be working on this again, starting from the most recent ones.
DONE 2011 Ray Kurzweil (From Eliza to Watson to passing the Turing Test) CURRENTLY WORKING ON 2011 Stephen Wolfram (Computation and the future of mankind)
Here is an index of all Singularity Summit speeches.
Summit 2006
Summit 2007
Summit 2008
Summit 2009
Summit 2010
Summit 2011