Pragmatic Marketing is a company that teaches software product marketing seminars. And the publish a truly great magazine on product marketing. Yes this is a relatively obscure field, and these folks execute well in that area.
The good news is their magazine is free as are the resources on their web site. The seminars appear to cost about 2 to 3k which is not for every start up. Yet if you are designing software products for the open market, perhaps worth the investment?
The image is the Pragmatic Marketing grid from this PDF on their site.