I figured I'd try to pick an SEO-rific title to hopefully convey the steps I went through to migrate data from a WM6.1 to WP7.
My Prerequisites: (yours may vary) Outlook and Outlook Connector, OneNote 2007 optional. Thunderbird also works great or so I've been told.
This post assumes everyone has already setup the activesync between their computer and the wm6.x device and the data they want is synchronizing to Outlook. Alternatively I also had the Windows Live app on the phone which allowed for direct synchronization to Hotmail but at the time I didn't want to clutter it up with all my IM email addresses. Skipping Outlook or Thunderbird would be the easiest approach obviously but I found Outlook to be a nice data silo and I could've chose to sync my limited phone number data to the lesser used cloud service.
You have two methods of import, People settings and Email. For the most part the consensus seemed to be to use Settings -> Email & Accounts and People as a la ...