Working primarily in B2B over the last few years LinkedIn has often been the social network of choice.  I came across a great browser plug-in today called Who Works At.

It's a plug-in for Chrome.  With it installed you can tell who works at whatever website you are currently browsing.  So if you're on Google, you can click the button and it will reveal who on LinkedIn works at Google.

I installed it a minute a go and it doesn't work perfectly, but I'll play around with it some more and see if it improves.  In the meantime, here's a video explaining how it works.