Hi Jim. Here's a link I found when browsing. I think that they are forgeable, but with a lot of extra effort. I have some D-2. Heat treat may be tricky, especially on those steels which suffer from temper embrittlement. A very good idea that is by no means original is to get stock/uses that is close to shape so it requires little grinding. Also, people report some success with fabrication techniques involving brazing or stainless filler.
http://www.cashenblades.com/Info/Steel%20selection/Steel%20selection.html