Some useful Network Command

ifconfig - lists IP address (similar to ipconfig in Windows)
iwlist scan - shows wireless networks that are available in the area along with basic encryption information
lshw -C network - Shows interface and driver associated with each networking device
lspci -nn - Shows hardware connected to the pci bus
lsusb - Shows USB connected hardware
lshw -C usb - Additional info on USB related hardware (good for USB dongles)
cat /etc/modprobe.d/blacklist - List modules that will not be loaded by the Operating System at boot time
lsmod - lists currently loaded kernel modules. (Example usage - lsmod | grep ndiswrapper)
route -n - Lists kernel IP routing table -- Good for troubleshooting problems with the gateway (netstat -rn = equivalent command)
sudo route add default gw 192.168.1.1 - Example of how to set the default gateway to 192.168.1.1
sudo route del default gw 192.168.1.1 - Example of how to delete the default gateway setting
sudo modprobe ***** - Loads the kernel module **** . (Example usage - sudo modprobe ndiswrapper, sudo modprobe r818x, sudo modprobe ath_pci)
sudo modprobe -r **** - Unloades the kernel module ****. (Example usage - sudo modprobe -r ndiswrapper)
sudo ifup/ifdown - Brings up/down the interface and clears the routing table for the specified interface
sudo ifconfig up/down - Brings up/down the interface for the specified interface
sudo dhclient - Request IP address from DNS server for specified interface
sudo dhclient -r - Release IP address associated with specified interface
sudo iptables -L - Lists firewall rules
dmesg | more - Lists boot log -- good for troubleshooting problems with modules/drivers not being loaded
uname -r - Displays kernel version
/etc/iftab (Feisty and pre-releases (Edgy, etc)) - /etc/udev/rules.d/70-persistent-net.rules (Gutsy) - File which assigns logical names (eth0, wlan0, etc) to MAC addresses
cat /etc/resolv.conf - Lists DNS servers associated with network connections (Network Manager)
/etc/dhcp3/dhclient.conf - File which sets or modifies dns (domain name servers) settings