Hi Richard Cranium
... is it possible to configure TC to act as a router? ...
Yes, it is. Is it worth the effort? Probably not. I've picked up 4, 6, and 8 port
routers for $5 each at garage sales. If you want to build a 4 port router, you
need 4 network cards for the ports plus a fifth network port for the internet
connection.
If I were to attempt this (which I wouldn't), I would google:
linux open source router
and use one of the existing router projects out there.
... set up a file sharing service?
File sharing is easier. There's samba3.tcz to share files with Windows.
If you install cifs-utils.tcz on your Linux machines, they can access it too.
There is nfs-utils.tcz if you only want to share with Linux.