) is a community-run technology news site, one of the first of its kind. Users submit stories (links to news articles, press releases, and their own reviews and editorials) to a central core team of administrators. A handful of these submissions get chosen for posting on Slashdot's front page. Users can then comment on the stories and reply to other comments. What makes the system work is that there is a moderation system in place which allows users to rate each other's posts as being better or worse. Highly rated posts can be displayed first, allowing people to quickly read through the most relevant and informed commentary on the day's news. There is even a meta-moderation feature which allows people to rate how well the moderators are doing at rating posts: bad moderators are picked to moderate less often. As a user, if people rate your posts as being relevant and well-written, you gain "karma." If your karma is high enough, your posts are automatically given an extra point when you post (i.e., they are marked as being somewhat relevant before anyone has even moderated the comment).
Slashdot has opened its code (http://www.slashcode.com) and many other sites (like http://www.kuro5hin.org) run slightly modified versions of the code to produce their own community-run news sites. You can too, if you so desire!
Rusty dumped Slashcode after a couple months because he found it too "hairy". Besides, it wasn't publically released for a year. So he wrote the much better Scoop engine.
See also MeatBall:SlashDot.