I've updated my SharePoint resources page to include some more blogs and webcasts. I've also added a link to Lamont Harrington's SharePoint resource page which has a ton more resources that the page I created. Take a look.
Also I spoke with the WebCast guys at Tech-Ed and it sounds like there is an RSS feed in the works for webcasts (and it will probably have categories). So hopefully keeping a list of SharePoint webcasts will get much easier soon.