The first big reveal is that Fable 2 will have a mini-game released on Xbox Live Arcade a few weeks before the game comes out.  Money earned in that game will be available for you to use inside Fable 2.  The original fable has several gambling min-games to help you earn money.  Looks like this aspect of the game will be brought to you as Xbox Live arcade titles.

The second big reveal is that you will be able to play Fable 2 co-op over Xbox Live.  You will be able to have dynamic co-op where a friend can jump into your game with his/her character.  All items you gain in co-op will be available to you in your single player.  This is probably the best feature Fable 2 could add.  Co-op in Gears of War and Crackdown made those game so much more fun.

If you never played the original Fable it was my favorite game for the Xbox.  It's an action RPG that allows you to play good or evil and the game treats you differently by the choices you've made.  It's a great game and can be downloaded from Xbox Live Originals onto your 360.  Give it a try, it's a great game.