Can I use an old iPhone as an iPod Touch without a contract?

My old iPhone 3G contract will be expiring soon, and I plan on replacing it. Once I get a new phone with a new contract, can I still use the old iPhone basically as an iPod Touch? I want it to still run all the apps I have and still connect with WiFi. I’m not looking to jailbreak this one or use it on another network. I want to make sure this isn’t just a brick without a service contract! Thanks!