I've just finished my first fully iPhone enable web app (not to be confused with iPhone app which are installed onto the phone via App Store). It's here:
It's basically a wrapped version of Crosstips that uses these sample resources to imitate a native app but in the Safari web browser.
It works really well and wasn't too hard to do. I think the key is to remember that the iPhone Safari is after all a web browser but it also has excellent support for AJAX (and jQuery). There are probably some bugs that I have spotted yet and there is work on the optimization but for now I'm happy.
So, if you like to solve crosswords in bed and you have an iPhone then bookmark crosstips.org/iphone
Tried it on my Nokia e71, whose browser is also webkit based. The initial page displayed fine, but clicking on "Search" does nothing.
The search depends on an onclick which does a bunch of things including the actual AJAX request. Thanks for the feedback though.