Well, I builded up a SSO mechanism and a sync process to align users between DNN and Moodle.
DNN is the master site, so users join the system via DNN.
I developed a schedulable module that creates the same user (username and password) inside Moodle and, to do so, I used OKTech WS.
This module is scheduled to run every 5 mins and syncs only newer users (those who signed up "today"); of course I created another similar module to sync users in a batch way (sync all users that doesn't exist inside Moodle).
I used VS 2008 so .Net 3.5 and C#.
Hope this help but feel free to ask again if you need more help.