RMW Web Publishing has created a iPhone Tester that supposedly simulates the iPhone mobile web surfing experience. RW Web claim it works better using Safari. I tried it in Firefox for Windows and Safari and it did not pick up the mobile fix plugin for this site or other mobile ready sites I know off. Though it did render their example site perfectly. This leaves a couple of questions open to hwo the iPhone is rendering mobile web ready sites. I have not actually tried the iPhone as it is not available in Europe yet.
Feel like trying out the iPhone simulator then head over to http://iphonetester.com and kick the tires. Some of the buttons do not work on the simulator and it claims there are more features coming soon.