AirWaves is a desktop application for instant messaging, that will be integrated with Facebook for video chat and messaging, among other features. It's currently still in development.
Built using Adobe AIR, this application looks like it will be similar to the Yahoo Messenger Vista. If done well, it will be a way to bring some Facebook functionality to a desktop client, in what looks to be somewhat close in concept to the way 8hands brings your MySpace account to your desktop. AIR, formerly known by its code name Apollo, has recently launched some features to encourage use by more developers, including the ability to create AIR applications directly in Dreamweaver, circumventing the need to develop withFlash.
A Meebo Facebook application enabling friends to chat with each other directly on their Facebook profiles has also been created. While it doesn't look like AirWaves will be used as a Facebook application, it will be an interesting integration of Facebook capabilities, nevertheless.