Since IronPython is a implementation of Python 2.7, any Python documentation is useful when using IronPython.
IronPython's sweet-spot is being able to use the .NET framework APIs directly from Python.
IronPython in Action by Michael Foord and Christian Muirhead, offers a comprehensive, hands-on introduction to IronPython for programming the .NET framework.
When all else fails, you can always look at the source code.
Builds - Recent builds on the CI server