If you are an Android user no matter the carrier you are on and want a VoIP app that is better than Skype, Fring is coming soon. The app is carrier agnostic and will allow you to make calls to landlines from within the Fring IM app. The company is growing quickly and is said to be adding about a million new users monthly.
Fring is interesting for many Android users because in addition to making phone calls it also supports IM on most services. Supported services include MSN, Yahoo, AIM and others like Jabber. Fring also supports video conferencing.
That video conferencing solution doesn't require the person on the other end to be running Android, unlike other video conferencing solutions. The app lets the Android user video chat with any front facing camera device like Nokia smartphones and the iPhone. I would assume those devices need the Fring app installed as well for video chats.