I'm not sure right now where to find the links to the archived versions, the Training and Events link seems to not have any of the webinars, but for those of you who didn't catch the "Optimization Techniques II: Optimizing a Convolution Algorithm" one on the 8th, you really should.
The presenter was very good, and the depth was awesome, I think I learnt more in that one about the "why do" OpenCL than all the others. Well, to be fair to the others, they were far more introductory, so I guess this one had the benefit of jumping right in to the meat of it. I got something from all of them, but that one in particular I thought was very helpful.
Still wish there had been enough time to investigate the CPU side of things more than they did...