T-Mobile's Bobsled app, which was announced in April and gave free Internet calling over Facebook to the masses (non-T-Mobile customers included), was a cool idea. But it struggled after Facebook temporarily pulled the plug— intoducing its own VoIP solution with Skype shortly thereafter. Now, though, Bobsled is back, and T-Mobile has triple reinforced the service with versions available for the browser, iOS and Android.
Calls made via Bobsled are free to any number in the US, Canada or Puerto Rico, regardless of what country the caller is in. When you receive a call via Bobsled, all the devices on which you've installed the app will ring at once until one of them is answered. The service even supports text messages, and you can call any of your Facebook friends and leave a voicemail that will appear as either a wall post or message in their inbox.
Check out the new Bobsled for yourself here.