I'm also a big fan of the talk on persistent data structures, simply because it was my first introduction to them.
"Are we there yet" is also great: http://www.infoq.com/presentations/Are-We-There-Yet-Rich-Hic...
I also love "Hammock Driven Development": http://www.youtube.com/watch?v=f84n5oFoZBc
I'm also a big fan of the talk on persistent data structures, simply because it was my first introduction to them.