We were talking last night about extracting mood data from twits (the opportunities for extracting sarcastic puns are too plentiful and obvious to pursue). Here's a link to a movie of the US map showing how twit mood alters over the course of the day. The states are distorted in size according to the twit volume and coloured from green (happy) to red (unhappy). It's fun to watch. http://www.ccs.neu.edu/home/amislove/twittermood/
I found this link reading a paper about extracted mood data from twits to predict stock market movements. Here's a link to the paper. http://arxiv.org/abs/1010.3003