Wow, this has been on hold for ages! I know I could have used this information in the past, and several people have asked me about this.

Perhaps there should be a place in the documentations which explains how sys.path is populated, with detailed explanations for different platforms?

With some guidance as per the right place in the docs for this, I'll gladly work on this. Note that I'm not an expert on this issue, I just plan to gather information form several places and write up a single nice documentation page.