<p>As the question states - is there a good tool out there which lists methods an unmanaged DLL exports? I would like it to list COM methods and interfaces too.</p>

Take a look at
Dependency Walker
to get a list of unmanaged functions exported from a DLL.
You can't easily get a l list of COM classes exported from a DLL. What you'd have to do is something like to through the registry and find all objects that reference the DLL in question. DLLs advertise their classes via registration in the registry...