Remember when Apple almost bought Be, which would have made BeOS the foundation for the next generation Mac OS? Apple bought NeXT instead, and BeOs - which many of us fiddled with - eventually vanished.
It's back, but with a new name. Since 2001, the Haiku project has been developing a free, open source operating system compatible with BeOS - and it's finally reached the alpha stage. If you have an old PC or have virtualization software on an Intel-based Mac, you can download the ISO, burn it to a CD, and use that to boot and install the Haiku OS.
Six years ago I bought an inexpensive used Dell Optiplex GX1 with Windows 98, because Yahoo Messenger had some capabilities on Windows that it didn't have on Macs (voice chat, for instance). That machine has been sitting unused for several years, so I burned a Haiku disc, booted from it, wiped the hard drive, and installed Haiku. A 450 MHz Pentium III machine with 128 MB of RAM certainly isn't the ideal platform, nor is a 640 x 480 display terribly practical nowadays, but I can report that Haiku runs reasonably well and looks very nice.
Unfortunately, I can't get it on the Internet yet. I don't know whether the built-in ethernet port is the culprit or if it's Intenet sharing on the eMac in the basement that's causing the problem. I'll have to try connecting another machine via ethernet and see if that works.
Haiku recommends more RAM and more CPU power than I have. It seems to support almost every PCI ethernet card tested, so that's an option if the built-in ethernet is the problem. For about $50 I could make this machine much more capable.
If you're looking for something new to play with, give Haiku a try.