Peter Wieland has started a blog.  Peter sits around the corner from me and works on UMDF (which exists under the WDF banner alongside KMDF).  He has written 4 (so far) excellent entries on DMA, part 1 is here.  DMA is one of the aspects of writing a driver that I did not know much about (I never had to write a driver which performed DMA) and his articles taught me a lot.