Reading Usable Help
@UsableHelp on Twitter
Gordon R. Meyer
More examples of supplemental Help
Cousin Michael's Publish Guide, Intelligence Assistant's DVD Companion and Recipe 4 DVD's DVD Companion are examples of using Help systems as a publishing platform. (See also Kirby's Help Offers Plug-in Notes.)
I think the opportunity to provide supplemental Help content is something that more authors could tap. I'm waiting to find the non-commercial experts who use this method to spread their good name and skill.