I have two Linux boxes. One is running KNOPPIX and the other Ubuntu. I have only one wifi dongle between them, and only one of them has an Ethernet port. They both have free USB ports however. I need the box with the dongle to share the connection through a male-to-male USB cable.
I know it is possible to do a similar setup with a desktop and certain portable devices, but I need it between two normal computers. I cannot buy any additional hardware.