The "Quarantine" label on the inside of the hatch is pretty obvious. It's sealed to protect the guy inside from what's on the island, not vice-versa.
The numbers. They're everywhere. The lottery numbers are on the drug vials. The lottery numbers total up to 108 (the graffiti on the wall in the hatch). The flight number is the same as the the time that the guy in the OR died.
The dead guy is "Rutheford," Shannon's last name. There's some argument whether Rutheford is her married name or maiden name, I'll wait to see how that plays out.
Desmond? Desmond? Desmond was talking to Jack in LA just a few years ago, but he's in a 80's retro apartment in the hatch. The automated series of mirrors to make his periscope work are intriguing, and indicate there are more exits. I'm thinking he hasn't been there that long, which means he got there long after Danielle.
Speaking of which, Hurley didn't mention to Jack that Danielle also knew about the numbers.
There's something about Sarah being able to move her toes. It's the same thing that happened to Locke.
I don't think there are any coincidences in LOST. I have to wonder how much in the series (like the lottery numbers) started out as coincidence and when the writers noticed it changed into something important.