I wrote about a couple of super-easy sites to create instant private chat rooms in my The Best Online Tools For Real-Time Collaboration. Robin Good reports on another one that is almost identical to the two I reported on my list.
It’s called Talck, and the only difference I can see from the others is that Talck’s home page is in Spanish. But you certainly don’t need to speak that language in order to use the service. Like in the others, all you do is type in the name you want to call your chatroom, let others know about it, and chat away.