In addition to the obvious uses for LinkedIn ( searching for job, checking out employee prospects, getting questions answered) I came up with a new use for the site today.
Today was the kickoff meeting for the MESA Lean Manufacturing Working Group (it is actually much more interesting than that sounds, but probably more geeky) and after the meeting I went out to LinkedIn to connect with any of my new teammates who were on the site. After some discussion and thought, it became apparent that one of the team members was also a perfect contact and information source for an issue at work (although unrelated to this working group). I confirmed this with him after the meeting and decided having my boss and my grandboss in the teleconference next week was more efficient. Normally I would have written up an intro and overview on his background, relevance to the problem, etc. In this case, since both my boss and my grandboss are connected to me on LinkedIn, I just forwarded them his profile link with a quick note. Hardly any writing on my part, and lots more information than they normally would have gotten the old manual way.
I know there are a bunch of people out there who say all they do is multiply connections on LinkedIn and never really use it, but the more time I spend there, the more useful I find it.