Online newsgroups are popular gathering spots; over the years they've logged millions of opinions on topics ranging from politics to appliances. The largest newsgroup network, Usenet, boasts 500 million messages posted since 1995; unlike postings in chat rooms and online forums, such messages tend to be uncensored-and preserved.

All these postings add up to a trove of public opinion that sociologists, linguists and market researchers would love to analyze; and software projects at IBM and the University of California at Berkeley are beginning to develop the analytical tools they'll need. Unlike Web search engines, which try to find the best matches for any one query, these efforts focus on understanding how communities of individuals interact online, and how their opinions evolve.