I've been using LinkedIn as a passive repository of my face-to-face network. Occasionally, people find out we have a common acquaintance and that's fun to know. Not a life changing application for me.
I've been wondering whether I should/could use LinkedIn in more ways. Friends told me that they find/receive CVs of interesting candidates through LinkedIn. Get in touch with conference organisors etc. A new teacher at the Masters was found through LinkedIn contacts.
Though I never have to find candidates for vacancies, we recently looked for a partner for a consultancy, using our good old face-to-face network. We found a great one, but it would have been a nice experiment to try and use LinkedIn.
Commoncraft has made a video about LinkedIn. (their videos hardly need to be spread as they are widely known by now). However, I liked this video about LinkedIn because it doesn't explain the basics of LinkedIn but explains how you can use LinkedIn to facilitate your work.