Steve blank's blog is a virtual treasure trove of these insights. www.steveblank.com
Eric Reis takes Blank's CD model and extends it into actual product development...where the discussion is much less "Why?" and more "How?" www.startuplessonslearned.blogspot.com
You can also get Steve's book on Cafe Press and Amazon. (can't get it at B&N or Borders) http://www.cafepress.com/kandsranch http://bit.ly/1m4R1S