Think of the hobbies and activities you enjoy to do in your free time. Surely you have a wealth of knowledge about these areas that others might appreciate gaining more insight on.

I think this is a very helpful and inspiring of your post, but as @cicisaja said... what about the interaction and communication skill? I saw many great and talented businessmen fails to keep their inetraction with end user. sometimes when you put yourself as an expert and hope for the higher recognisition of other people, you've just to busy to answer their questions because you've already write it down on your book while not everyone get an acces to that book. Thanks God there's internet.. but still, interaction still the great barrier to reach the expert too, what do you think?