This is an amazing FREE app that's been around for awhile but has flown under my radar until today.
It's basically an instant messaging client which incorporates pretty much any kind of instant messaging type out there - MSN, Google Talk and Skype being the main and important ones to me. What it does is gather all your contacts from these services (your own phone contacts included) and puts them into one fat (but centralised) list.
The killer feature : voice calls over 3G!!! I was playing around with it this afternoon with my uncle, and grandpa, and it works really well!
For skype contacts, you can call to any iPhone or computer running skype.
For MSN contacts however, I noticed unless the other person is using Fring, you can't call them.
Another cool thing is that if you are on Skype on a computer with a webcam, then the person on the other side using Fring can see that webcam feed! The actual Skype app doesn't even support this!
Also when you close the app you will still be signed in so you will get notifications when people send you messages or try calling you.
The best thing about it: ITS FREE!!! So get it right now!
The worst thing: the annoying tone it makes whenever you get a message....but easily overlooked for its amazing features.