I think that Jon Snook would be a great speaker on a number of different topics including design, Javascript, php, Adobe Air. Not only has jon created a bunch of web apps and mashups himself, I think he could also provide a great insight into his ideas process, and how to flesh out the ideas into final products.
As I mentioned in one of the other topics, I think that many of us, if not most of us, now have a strong grasp of HTML/CSS/Javascript/server-side skills but could use guidance and inspiration on how to take these skills, build something that matters and get it out there, and I think Jon has experience in this area that he could share.
(Rather than make a new idea topic, I'd also like to suggest Shaun Inman and Dan Cederholm for the same reasons.)