A piece of commercial software made to host discusssions; it can be used for conferencing, or virtual collaboration with asynchronous communication. Caucus runs on the most common Unix servers with Apache.

In the end, AFAIK, it's the single piece of software that most closely resembles a BBS in these modern days.

There are a few noticeable Caucus sites out there, mostly:
- Howard Rheingold's Brainstorms, and
- The Twin Cities FreeNet