The first lecture was the keynote at the FreePlay conference, a couple of weeks ago in Melbourne. The lecture is about how to minimize risk and maximize quality as an indie developer, while creating art instead of products; also, it goes pretty deeply into my views about what we could/should be doing as game designers. Sumea, an Australian game developer portal, has posted the video on this page (here is the direct download link; it’s about 92MB).
The second lecture was given in March 2007 at the Indie Games Summit (at the GDC). This talk is more about prototyping; it shares some material with the FreePlay talk, but has a bit more in terms of game demos, and a heavier emphasis on details about Braid (though the version of the game it shows is much earlier). Here is a download link to that one (.mov format). I would provide a Google Video link but WordPress is being lousy and stripping out necessary things from the tags (why would it do such a thing?)
If anyone wants the PowerPoint slides to either of these lectures, leave me a note and I will become motivated to put them up.