I've just been advised of a utility called iPhoney.
No, this is not an iPhone simulator, but it is intended for web developers who want to see what their sites will look like on screens with the exact dimensions of the iPhone's screen. That'd be 320x480.iPhoney requires Mac OS X 10.4.7 or later.
With iPhoney installed, you can:
- Test your iPhone-enabled Web 2.0 applications and compatible web sites.
- Open any website that works with Safari (use Safari 3 beta for the most accurate experience).
- Rotate to see websites in either portrait or landscape orientation.
- Show or hide the location bar for a full-screen iPhone experience.
- Simulate the iPhone user agent, to test browser redirection scripts.
As I said, not an actual iPhone simulator, but kind of an iPhone simulation of a simulator.
Download iPhoney here.