I don't have an iPhone. Nor do I have an iPod touch, which offers the same basic Web browsing features as the iPhone. But I still want to see what our Web sites look like on an iPhone, for obvious reasons. I'm sure I'm not alone, and there are plenty of Web designers out there tasked with developing sites that are at least readable on an iPhone, but whose managers won't actually spring for an iPhone or iPod touch.
Thanks to iPhoney, a new open source browser developed initially by Marketcircle, you too can browse the Web in the full 320 by 480 pixel glory of the iPhone. You can rotate the display by choosing Window > Rotate iPhone, and from the iPhoney application menu, you can choose the Web Kit user agent, the iPhone user agent, or a custom user agent (one of which might be necessary to convince your site to show you the iPhone-specific styles or content). Other than that, you can zoom in and out, enter new URLs, go back and forward, and view the source of the current page. It's pretty simple, but for checking how sites will display, iPhoney seems like the real thing.
And before you ask, no, it is not an iPhone simulator. It's just a Web browser that happens to look like the iPhone.