How do I route a spare network interface through an SSH tunnel?

I just bought a Raspberry Pi and I am wanting to route an ad hoc wireless network interface fully through an SSH tunnel that was created using another wireless interface. I want to do this so that I can have a secured and private connection to the internet at places with public WiFi. I know this would be easier to do all on one computer, but I would like to have it on the RPi too since I use it for other network related things when I am using the internet, and then just simply connect to the ad hoc network from my laptop/phone. This will really help me with my iPhone because it does not support an SSH tunnel locally. How should I go about doing this? Thanks in advance for all of your help.