Skype, the eBay (EBAY)-owned service used by more than 338 million people to make free PC-to-PC calls, later this year plans to release a new product called "Skype for your mobile" that will let customers use local wireless minutes to make international calls. And that would take big bites out of wireless providers most lucrative traffic.

...offered through Apple's iPhone App Store. Truphone is one such tool. When used on Nokia (NOK) e61 and Nokia n95 smart phones, the British-developed service lets users make calls for a few cents a minute using a data plan rather than wireless voice minutes. Calls to other Truphone customers using Nokia N-series or E-series devices are free. So in theory, a user could save money by purchasing an unlimited data plan in tandem with the lowest-priced voice plan necessary.