<p>I am looking for details of the VTable structure, order and contents, and the location of the vtable pointers within objects. </p>

<p>Ideally, this will cover single inheritance, multiple inheritance, and virtual inheritance.</p>

<p>References to external documentation would also be appreciated</p>

<p>Documentation of GCC 4.0x class layout is <a href="http://www.cse.wustl.edu/~mdeters/seminar/fall2005/mi.html#virtual" rel="noreferrer">here</a> and the Itanium, and more broadly GNU, ABI layout documents are <a href="http://www.codesourcery.com/public/cxx-abi/abi.html#general" rel="noreferrer">here</a>. </p>

Most of the compiler implementations that I have seen just "embed" the base object into the derived object. It becomes irrelevant where the vtable is kept because the relative offset into the object will just be added at compile time as references are evaluated.
Multiple and virtual inheritance are more complicated and can require a different offset depending on what is being accessed.
I highly recommend reading this article on Code Project:
The Impossibly Fast C++ Delegates
It brilliantly gives a broad picture of how different compilers handle various aspects of inheritance. Fantastic read if you are interested in the low level workings of different compilers.
Edit: I linked the wrong article over there. Corrected.