iPTT

Push-to-talk is probably the most effective way for a group to communicate in realtime, and iPTT delivers just that (and more). iPTT is a simple but powerful push-to-talk app designed for the iPhone and iPod Touch . Whether you're interested to socialize, discuss special interests or as productivity tool for your teams, iPTT has been built with your needs in mind. And unlike traditional push-to-talk networks iPTT's network spans the entire globe and joining is currently free!

iPTT features two modes: Public and Whisper. In Public mode everybody on the channel you're tuned into will hear you when you speak (aka having the floor). Whisper mode, on the other hand, allows for private one-to-one conversation between individual users on the same channel.

So give iPTT a try and let us know what you think, and don't forget to tell your friends about it.
Over and out!