For a US IP address you can use HotSpotShield.
It's free and you can either install the application ore
follow the instructions for the iphone an use them in your vpn settings.
Witopia is great, servers in many countries, OpenVPN or PPTP (OpenVPN much better, although PPTP works easier on iPhone), good pricing, and awesome support....
It all depends what youre looking to do with it. For simple anonymous browsing, some providers offer this for as little as $5/month, or even for free. But if you want a total Internet traffic anonymizing experience, a premium VPN account is a better way to go - theres no IP numbers to configure into the webapps, and no software to install - just set up the VPN and its done! Other VPN selling points include: