I’ve just finished posting three reprints from back in 1998 and 2002 when I was working on lots of COM stuff.
Sinking connection points in C++ objects - shows you how to use the least COM possible to connect to Connection Points and provides a C++ template that does all of the hard work for you.
Designing asynchonous COM components for VB - This example COM component provides three COM objects for using the Win32 Mailslot IPC mechanism. The component may be useful if you need to communicate from VB using Mailslots. However, the reason I wrote it was to demonstrate creating a COM component in C++ that integrates well with VB and can fire asynchronous events.
IEnumXXXX - COM objects generally provide access to sequences using an IEnumXXXX style interface, this class wraps that with an STL style iterator.