The iPod Touch is pretty much an iPhone without the 3G cell-phone hardware inside, but now you can download free Truphone software that will enable you to make telephone calls with it. The only thing you’ll need to buy is a headset.

Truphone uses the second-generation iPod Touch’s Wi-Fi connection to make free telephone calls to other iPod touch owners, customers of Truphone’s VOiP service, and to uses of the Google Talk instant-messaging service. Truphone plans to expand its service soon, adding support for making low-cost calls to landline phones (a Truphone account will be required), free instant messages to Skype and MSN, and free calls to Skype and MSN users.

Truphone currently charges its customers $0.06 per minute to call landlines or cell phones anywhere in the U.S; text messages (SMS) cost $0.20 each. You’ll find their rates for other destinations here.

Truphone points out that its service shouldn’t be considered a replacement for ordinary telephone service, primarily because it can’t be made to make emergency phone calls. If you own an iPod touch and are interested in checking the service out, you can download the free software to your device from Apple’s App Store.