I can recommend Xabber, a client rich in functionality which was supposed to have its source code released, but I don't know what became of that. It works well, has logging and contact list integration (which almost works).
There is also Yaxim, which is completely free and works well but doesn't come with any of the extra functionality.
Those are all chat only. Voice and video chat is probably better served using SIP on Android as there is some native support for it.