Where does the iOS Simulator save screen shots?

Press Command+S. The screen shot will be saved on your desktop.

iOS Simulator screen shots are saved to your desktop (~/Desktop). The file names are of the form iOS Simulator Screen shot Feb 28, 2012 12.16.23 PM.png.

You can also choose Edit > Copy Screen (default shortcut: ⌃⌘C) to copy the screen shot directly to your clipboard.