Skype for Android + IM + much more = Fring
Making free Skype calls from a Wi-Fi connection on your handset is a pretty neat feature in itself, but Fring aims to be a universal call and chat coordinator. It works just as expected, over EDGE, 3G, or Wi-Fi.
Twitter is also integrated, and it looks like the fring app works with any version of Android.
Download Fring Voip App for Android phones
Fring for Android can be downloaded via Android Market, or directly to your phone via Fring’s WAP site at m.fring.com Along with Android, Fring is available for iPhone, Windows Mobile, and Symbian phones.