You can setup ad-hoc networking to make two computers communicate or share an internet connection. The following scripts serve as an example. You will have to change the interface names for this to work on your system.
On the server
The server script works for a wireless card with an atheros driver. To make it work with a different card is trivial. More info there: https://help.ubuntu.com/community/WifiDocs/Adhoc. If you just want to connect two computers with no sharing of internet connection, you can leave out the iptables bit in the server script.
#!/bin/bash ####### this part should change or simply be removed depending on the network card #recreates the ath0 interface in ad hoc mode modprobe -r ath_pci modprobe ath_pci autocreate=adhoc wlanconfig ath0 destroy wlanconfig ath create wlandev wifi0 wlanmode adhoc ####### #starts the ad hoc server ifconfig ath0 down iwconfig ath0 mode ad-hoc iwconfig ath0 channel 4 iwconfig ath0 essid 'mine' ifconfig ath0 10.0.0.1 up #forwards the ad hoc network to the router iptables -A FORWARD -i ath0 -o eth0 -s 10.0.0.0/24 -m state --state NEW -j ACCEPT iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A POSTROUTING -t nat -j MASQUERADE sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"
On the client
Run the following on the client. If you want multiple clients, you will have to change the IP address to be unique.
#!/bin/bash iwconfig eth1 essid mine iwconfig eth1 mode Ad-Hoc ifconfig eth1 10.0.0.2 up route add default gw 10.0.0.1
To share an internet connection, you need to tell the clients about the DNS servers. See the /etc/resolv.conf file on the server.