Are there any resources or guidance out there on how to make iPhone friendly web applications?
In my case specifically, I'd like to use ASP.NET MVC, but since that all runs on the server, I know it'll boil down to just markup/css/javascript considerations.
edit: as I find other resources not mentioned here, I will update the question text :-)
Scot Hanselman had a great presentation at Mix 09. Click here link.
Also look at the Mobile Device Browser File=>LINK. It is open source at codeplex.
"What is the Mobile Device Browser Definition File?
The Mobile Device Browser Definition File contains capability definitions for individual mobile devices and browsers. At run time, ASP.NET uses this .browser file, along with the information in the HTTP request header, to determine what type of device/browser has made the request and what the capabilities of that device are. This information is exposed to the developer through the Request.Browser property and allows them to tailor the presentation of their web page to suit the capabilities of the target device." - Codeplex
There’s an iPhone article on Sitepoint (which usefully shows you how to target stylesheets at just the iPhone, whilst hiding them from Internet Explorer—Apple's documentation doesn't).
Craig Hockenberry wrote Put Your Content In My Pocket at A List Apart.
A Flickr developer posted some lessons learned: http://code.flickr.com/blog/2008/10/27/lessons-learned-while-building-an-iphone-site/
+1 for Apple’s documentation as mentioned by Boot To The Head—horses’ mouth and all that: they have pretty comprehensive stuff on neat CSS properties that are only really supported by Safari, like CSS animations and CSS Transitions.