The free "1000 Club" DLC is live today for Forza Horizon. Essentially, it's a challenge mode that tasks you with besting literally 1000 tasks, with every existing car in the game. There's speed tests as well as other technical challenges, and the DLC itself comes with two cars (the RUF CTR2 and the 1956 Ford F100).
Once downloaded, the game will suggest challenges for you based on the cars you have available. This is a pretty sweet addition if you ask me, and a decent start in offsetting the offensively priced $49.99 Season Pass.