Unlocked iPhone: What's the cheapest plan out there?

[Velocity]

So for someone with an unlocked iPhone, what's the most affordable plan available beyond the AT&T web that still provides internet access?

[Limelight]

tmobile, it needs to be GMS and tmobile is the only one that is GSM. Don't get it iphone sucks. It doesn’t have anything. Its all hype. It can't text pictures, it can't record video, it had connection issues, no mobileTV, no ATT services, most apps are pointless and dumb, no external memory so your stuck with your limit, too itunes centric, low speakerphone, no bluetooth, no flash for its web browser so your stuck with just youtube for videos, and the camera doesn’t have any features or flash. No zoom, no color effects, no frames, no brightness settings, no built in FM radio, too many people have it, it ends up costing more in plans, it doesn’t have a slot for cell phone key chains, it is really hard to text on the digital QWERTY keyboard, no TTY support, kinda dull looking. It’s no good SOO overrated. So many better phones out there.