I'm new to 3d gaming and unity, but I'm not new to Javascript. I'd just like to create a 2d game with some physics and integration with gamecenter (it'd be on the iPhone by the way).
Where's the best place to start? There's a ton of stuff, but I don't see many tutorials for a 2d iPhone game.
You don't see the tutorials because Unity isn't a 2D engine. All the "2D" Unity games you might see are "fake 2D". That is, people are using textured quads with alpha masks. Games with a 2D look are very doable, but you still need to think in 3D in order to layer things appropriately. Here is the closest thing Unity Technologies provides for you. You should be able to extrapolate some concepts from that, to work with more "flat" objects.