...or, even better, both!
Here's what I'm planning on doing with our old 8600 when the new Quicksilver turns up

:
2 Enet cards (which it has already) + Vicomsoft Internet Gateway (or whatever they're calling it now) = router with NAT for my cable modem
Upgrade to OS9 to give filesharing over TCP/IP - this way it's compatible with the machines in the house that will be running OSX. I'll remove multiple users etc. to speed OS9 up.
Run RC5/OGR, but set to a fairly low priority aso as not to interfere with filesharing etc.
Add in VNC or Timbuktu for remote control and it can be stuck away under a desk and forgotten about. Bliss.
Alternatively:
Just have some fun with it if you can't think of anything useful. Try:
- Overclocking (if it's possible with a 7200?)
- Building a new case - I put my LC475 in a crate (that's still an ongoing project!)
- Bung it with a monitor and keypad or something into a box and ou have a basic arcade machine - relive those classic games!
Good luck!