Now that the iPod touch comes well equipped with two cameras and FaceTime abilities, those that were avoiding the iPhone because of the pricey data plan can continue to do so. Pinger, the brains behind Textfree [iTunes Link], says that it's offering a similar service for making phone calls. The calls can be made over a 3G data network or WiFi, which is great for iPod touch users.
Though it seems implausible that a company could afford to offer free text messaging and free phone calls, Pinger's business model relies heavily on that five-second window that a text message is sending or a call is connecting. That short period of time is prime real estate for advertisers, because if you want to continue to do these things for free, you might as well spend a few seconds looking at ads. If you don't want to bother with advertisements, you can also pay-per-minute, load them up on your account, and then make phone calls and send text messages that way.
You can download the Textfree app [iTunes link] to see how the free SMS works. Though there are currently no voice calling features, the application still assigns you a phone number based on your zipcode. We tried calling our custom number and it's sort of like a pager service that simply notifies your friends that you're looking for them. Pinger's website says that the voice calling features are "coming soon", so stay tuned.