iPhoney: It’s not quite a simulator, but will certainly help web developers understand what their sites will look like from an iPhone. Since the iPhone uses Safari, the iPhoney app can use the same on an OS X system to provide a pretty decent testbed:
Looking for a way to see how your web creations will look on iPhone? Look no further. iPhoney gives you a pixel-accurate web browsing environment—powered by Safari—that you can use when developing web sites for iPhone. It’s the perfect 320 by 480-pixel canvas for your iPhone development. And it’s free.