Altme, a private messaging system built using the Rebol language, has
released beta versions for Linux and Mac OSX. I have created a
"world", called "hyperworlds". If you want to join, email me with the
username and password you want to use. I will add you. Once logged
in, you can change your password. There are sections for sharing
files, a calender, checklists, and of course, chat. I have been
waiting years to try this out. I did try it out using VirtualPC on my
Mac several years ago, but couldn't keep Windows 98 running for long.