i was just playing around and i found an awesome way to dox someone who is in your skype contacts. this won't always work, but most of the time, it does!

method

1. go to facebook
2. click on your friends notification icon in the top bar, and click "find friends"
3. it will take you to a find friends page.
4. login with skype
5. it will show you the facebook profiles of your skype friends using their emails.
6. chances are, you can friend them, without them even noticing and let the doxing begin.

other things you can do
you can do this with tons of services like msn messenger, and aol.