Sketchcast.com lets you recording the entire sketching process (including erasing if you want) along with audio commentary. It is sort of animated whiteboard with voiceover. You can embed this sketching/audio recording in a blog YouTube style (click on the image above for a demo). It's an interesting idea. But, I'm not sure how broadly applicable it is since it is pretty hard to draw and talk at the same time in real time and produce a coherent presentation in one shot. Some sort of editing features are needed before longer form presentations can be made by most people (e.g., me).