Can I use iPhone as an iPod or Internet device without activating it?
Yes, you can use your iPhone as an iPod with WI-FI without cell phone activation, but you must have iTunes activation to download music through iTunes.
Your iPhone can be used as an iPod Touch without an active wireless telephone carrier. Using it as an iPod touch means that you can use it in iTunes. You will also have WI-FI.
According to the Apple website, you do not need a telephone service plan to use the WI-FI and iPod features on your device. If you no longer have phone service through cancellation, or if you have bought the newer iPhone model and no longer need your old one, there is a way to continue getting some use out of it, instead of just letting it lay around and gather dust. However, you do need to activate it on iTunes first.
If you have the older model phone, you must have the last used SIM card. ITunes requires this card for activation. After activation, you can remove the SIM card. You only need it for the activation process. If you don’t have the initial SIM card used with the phone, Apple suggests that you contact the carrier to get another one. Apple says that your “iPhone will be re-activated without phone service.”
If you have one of the newer iPhones, 3G or 3GS, you can use any SIM card that was connected with the last cellular service, even if it is from your new iPhone. You would activate it on iTunes the same way the older model is activated. Then you can take the SIM card out of your phone. Apple also says that if your phone has been unlocked you can use any SIM card.
You can get more information on this at http://support.apple.com/kb/HT3406.