For those not in the know, ELIZA was one of the first chatterbots -- she (or it) simulated human agency in conversations by acting as a virtual therapist. (You can see an AIM port version over at AIM ELIZA.)
As chatterbots go, ELIZA was fairly limited -- she had a pretty short set of responses, and more often than not, she would just repeat back what you said to her. But you could still have a fairly robust conversation with her, if you were stupid, distracted, or had a fairly forgiving nature.
In fact, you could say that ELIZA was the precursor to intelligent agents, as well as chat sex bots like Jenny18.
Back when I was working at AOL, I used to joke that ELIZA was more or less indistinguishable from some of our lower-functioning chat room denizens -- and arguably more useful.
While I'm on the subject -- I'm reminded by a situation we ran into with AIM Chats. Now, these days, AIM Chats are promoted group Web chats that are powered by Userplane. But, back in the day, AIM Chats were basically just buddy chat rooms, which were invoked via the URL (http://someAIMURL/chat+room+name).
Because they were promoted at a pretty high level off the AIM.com Web site, they were fairly high trafficked. I don't know if they were ever particularly useful, but they were pretty active.
Then the spam bots took over.
After a short time, you literally had rooms full of IM spam bots (usually sex spam bots) talking to each other. That meant that they were triggering a wall of sex spam IMs -- a bunch of bots talking to each other.
Then, occasionally, some hapless human would wander into the middle of this torrent of sex spam.
It was distressing, yet at the same time, hilarious.