com is a TOPS-20ish TALK (aka LINK) for UNIX. It basically links multiple TTYs together, though differently than in ITS or TOPS-20. It supports multiple public/private rooms, chat logging and automated cleanup.com runs on SDF.org
This article provides practical examples for 50 most frequently used commands in Linux / UNIX. This is not a comprehensive list by any means, but this should give you a jumpstart on some of the common Linux commands. Bookmark this article for your future reference.