A newsgroup is a discussion that takes place online, devoted to a particular topic. The discussion takes the form of electronic messages called "postings" that anyone with a newsreader (standard with most browsers) can post or read. There are over 10,000 newsgroups in existence, covering every imaginable topic. To find one that interests you, check out deja.com, a specialized database just for searching newsgroups.
Joining a newsgroup for research purposes can be tricky. Particularly contentious topics such as religion, gun control, animal rights, the death penalty, or race relations prompt postings full of biased opinion, misinformation, rumor, and general rantings and ravings. The best strategy is to read or "lurk" on a newsgroup first to get a sense of the credibility of the participants. If someone posts a particularly "expert-sounding" message with information you want to use, you might want to send him or her a private email asking about his or her credentials. Then try to verify those credentials, along with the piece of information, using a second source.