My previous post around the location and sensor platform in Windows 7 came a little bit out of context so apologies for that although I have since watched the PDC session and it's well worth watching.

However...if you want to start at the beginning with Windows 7 then there's the Developer Guide which you can download from here;

Developer Guide

and you should also make sure that you're subscribed to Yochay's blog which is up here;

The Windows 7 Blog for Developers