I love Wikipedia. I love using it, frequently spending many a spare minute (that I don't actually have) simply wandering from one entry to another, learning things I never knew I never knew. I love it, too, as an amazing example of why sharing and openness work. For those who aren't programmers, and who therefore don't grok the evident rightness of the open source methodology, Wikipedia is a great way of explaining how it's done and why it's so good.
On Open Enterprise blog.