Originally Posted by
BobbySteel
Sipdroid just launched their newest version which includes support for Google Voice via pbxes.org. It's a bit of a pain to setup initially but it gives you direct dialing via a Google Voice account, which is rather big. No ringback - total direct dialing out of the app.
But Android supports this out of the box.
In Google Voice, choose Settings -> Making Calls -> Use Google Voice to make all calls.