Who's using social media best for resourcing?

I'm on the hunt for examples of organisations who are using social media really well as a core part of their resourcing strategy - not just the ones who post on job boards or have a corporate blog, but those who have built a resourcing strategy that's actively delivered - at least in part - through a web 2.0 platform.

Loads of organisations are dipping their toes...and some appear to be drowning. Indeed, one wonders if the HR community should be tweeting, blogging and all the rest about their business at all?

I'm after some case studies - so if you have any ideas, please shout.