Does anyone know if I can buy a Nexus One and use it without a cell phone plan? Or if not, is there any Android phone that I can buy to use without a sim card?
You could certainly buy one and use it with a non-contract pay as you go kind of plan. To use voice, of course, you would need some sim card. Or do you want to just use it with wifi, like an iPod touch?
The Nexus One doesn't ship with a sim when you purchase the unlocked version. In that case it would be an iPod Touch... you'd rely on WiFi for all data usage.