[BeefWellington]

Having stopped writing COM components in the early 2000s, back then there were very good resources at Microsoft's site (MSDN) as well as within the Visual Studio help. It's interesting to hear it got worse just ten years later but kind of doesn't surprise me that they wouldn't upkeep that kind of documentation.

[HWR_14]

I did a COM project around the same time. It took a little bit of searching, but I found an excellent tutorial on a random site. Something that could not have existed at StackOverflow because it didn't answer a specific question, any question it answered would have been downvoted, and it would have been difficult to find there.