(You do not need crossover cables for this, a regular ethernet wire will work)
I know how to get wireless on xbox if you have a computer nearby with wireless connection..
and that is:
First connect an Ethernet wire to the back of your computer and then to the xbox 360.
Then Start->Connect To->Show Connections
After that click on the Wireless Connection, hold CTRL, and then click on the Local Area Connection that represents the port on the back of your computer.
Finally Right Click (on either the LAN or Wireless Connection)and Bridge Connections in 1-3 minutes you will be connected to live.