I am about to build a piece of a project that will need to construct and post an XML document to a web service and I'd like to do it in Python, as a means to expand my skills in it.  
Unfortunately, whilst I know the XML model fairly well in .NET, I'm uncertain what the pros and cons are of the XML models in Python.  
Anyone have experience doing XML processing in Python? Where would you suggest I start? The XML files I'll be building will be fairly simple.
I strongly recommend SAX - Simple API for XML - implementation in the Python libraries. They are fairly easy to setup and process large XML by even driven API, as discussed by previous posters here, and have low memory footprint unlike validating DOM style XML parsers.
XML Processing in Python