HardwareBook also has cable instructions.

You could use SLIP or PPP to connect to a PC. If the PC is running Linux or another Unix variant it's quite easy to setup a ppp server. On the mac it should be as simple as setting up a dial up connection with no number and no chat.

From there you can use whatever internet protocol to share files, including appletalk, there is a server for Linux called netatalk

You can also tell the PC to do NAT for the mac to share its internet connection...