Via his Twitter account.
2. Year One
3. The Killing Joke
4. The Long Halloween/Dark Victory (Cheater)
5. Grant's (Morrison) run
6. Gotham Central (All of it I guess?)
7. Arkham Asylum: A Serious House On a Serious Earth
9. Tower of Babel
10. The Cult/Year 100/Dark Knight, Dark City/Venom (Cheater)
I'm really surprised Hush & Dark Victory is there. Not that they're awful stories, just that they don't differ much from TLH. And while the Killing Joke is probably the most famous Joker story of all time, I think there are a lot of better ones. Dini's "Slayride", for example. I thought this was pretty interesting because Snyder's favorites will most likely play into the way he writes Batman (and probably already has).