The Battle of Forli will be the first piece of content, released in early January for the reasonable price of $3.99. It will involve Machiavelli and Caterina Szorza fighting alongside Ezio to protect a piece of Eden from the Orsi Brothers and the Templars. It contains six new missions, one of which will use the flying machine that players controlled briefly during the main campaign.
Bonfires of the Vanities is planned for late February and costs $4.99. This will open up a sector of Florence previously roped off (yes they closed off part of the game to sell it you later, it seems) and revolves around the monk Savonarola. Ezio will be eliminating this tasty monk's gang over the course of ten missions, armed with a new spring-jump move.
Seems like a good batch of content for an awesome game. Assassin's Creed 2 was a damn fine title and I'm totally stoked about getting back into Italy for some murdering shenanigans. I literally cannot wait.