Moving Windows Media Player song ratings into iTunes
I've finally figured out how to do it. I haven't written the code to make it happen yet, but that's the easy part.
iTunes exports a file called "iTunes Music Library.xml". This is an XML rendering of the music library - it's not the actual music library that iTunes uses, which means changing it won't do you any good, but you can Import it into iTunes. You can't just edit the XML file and then import it - you have to remove the song from iTunes before you can import it again, otherwise iTunes will skip it on import.
The Winter Fun Pack from Microsoft has a Windows Media Player plugin that can export it's music library as XML.
Now I just need to write some code to move the ratings from one XML file to the other.