Network Bridge comes in handy. Its essentially the same as ICS, only more flexible, albeit less secure. You might want to have a firewall remain on your system with it.
Normally, using a series of commands will work when bridge-utils is installed, but they're only for the current session. We want to make it permanent.
Procedure to follow
1. Get bridge-utils through Synaptic. This is the software we'll use to create the Network Bridge.
sudo aptitude install bridge-utils
Now, keep in mind to either print this out or not exit your browser, because in this next step we'll stop the Networking Services to change them.
2. Open a terminal, and type
sudo /etc/init.d/networking stop
Keep the terminal open.
3. Now we're going to edit our interfaces file:
gksu gedit /etc/network/interfaces
Replace whatever is there with:
iface lo inet loopback
iface eth0 inet manual
iface eth1 inet manual
iface br0 inet dhcp
bridge_ports eth0 eth1
Save the changes.
4. Now we'll restart the Network Services
sudo /etc/init.d/networking start
And there we go. Your computer is now set up to automatically share its internet connection without dizzying settings for more advanced set-ups!
Have fun, and note longer boot-ups will occur due to creating the network upon boot.