Seesmic for Facebook
An Adobe AIR app, Seesmic for Facebook (news) uses Facebook Connect to let you update your status and view friend status updates without surfing to the Facebook site. It's in beta testing, but it works as advertised: updating status is quick and easy, and whenever a friend updates their own status, it's there for me to see. It's a little buggy, but it was just released.
TweetDeck
TweetDeck is one of the most popular Twitter desktop clients, and now the app's developers are vying for Facebook dominance too. The upcoming version of TweetDeck lets you send a message just to Twitter, just to Facebook, or to both simultaneously. Once installed, the new version also includes a column displaying friends' status updates, and it offers the ability to chat with them via Facebook chat directly. The app isn't available to everyone just yet, but its public release is right around the corner.