I was doing a research on a COM interop question posted in microsoft.public.dotnet.framework.interop newsgroup. COM interop is known to be somewhat arcane knowledge, and MSDN seems to give only the very basics. However, there's this guy Aravind C who wrote a very detailed article on COM interop, and I recommend this article to anyone dealing with such bridging “in the trenches“:
http://www.codeproject.com/dotnet/cominterop.asp
There's another nice presentation on the same topic prepared by Andrew Troelsen himself (required Acrobat Reader or other software capable of displaying PDF documents):
http://center.org/p/docs/events/715/ComNetInterop.pdf