Interesting: a computer program which gauges the mood descriptions given by Livejournal users in every post. Updated in real time, this gives a good description of the feelings of a certain segment of the world's population (my guess as to the nature of this segment would be that it was mostly literate & computer literate, mostly below 30).

Examples: the release of the new Harry Potter book, people's drinking habits and, most interesting to me, the London bombings.