Difference between CPython, Python for .NET and IronPython?

[Carl Johan Rehn]

What is the difference between CPython, Python for .NET, and IronPython?

For example, if I'm running IronPython, can I access modules such as Numeric
and numarray?
 
As I understand it, interoperability with C# and .NET works in both
directions with IronPython, but CPython modules cannot be imported, or? 

With Python for .NET I can import the .NET Framework and continue using
CPython modules, or?

What is the roadmap for IronPython, will it be possible to import CPython
modules in the near future?

One last question, is IronPython cross-platform. That is, can I use
IronPython with Mono?

Carl