Is there an online resource with lots of iOS system icons? By this, I mean the dock, the "X" button for app icons, the lock screen slider, etc.

Any file format is fine, but I'd like them to be at least the normal resolution.
http://graffletopia.com/categories/macintosh
Looks like you'll need to get a demo copy of Omnigraffle to open them. Photoshop won't, and I'm not seeing other Mac standard software that will.  Also (Photoshop format):  http://www.teehanlax.com/downloads/