Bill Dudney, author of the "Writing Your First iPhone Application" screencast series, announced the availability of a free, 20-minute preview which goes into some detail on using Xcode and IB (Interface Builder) to build your first iPhone program.
iPhone SDK
Peter Wayner shares four effective iPhone application programming tools:
You don't need to master Cocoa and Objective C to create killer iPhone apps. Rhomobile, PhoneGap, Appcelerator, and Ansca tools leverage standard Web technologies and still tap native features
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Rhodes, PhoneGap, Titanium, and Corona are all good tools. Although there are differences in capabilities, your choice will probably rest with the one that supports your favorite language. That's the entire point of working with these frameworks. If you know JavaScript, Lua, or Ruby, you can create something on the iPhone very quickly.
iPhone Development Emergency Guide by Matt Legend Gemmell – This is the best guide so far, for "[...] competent developers who haven’t written code for the iPhone platform before, and just want to get started right now."
Palm needs a homerun, but bunted with the webOS SDK – Craig A. Hunter:
while the webOS SDK allows access to raw accelerometer data, it's limited to a 4 Hz sampling rate (that's four samples per second). Applications like gMeter and greenMeter need 50-100 Hz to even be practical, and most games need at least 20 Hz for smooth inputs that won't lag too far behind typical graphics framerates. A low rate of 4Hz is not usable for dynamic motion where high fidelity is desired. Accelerometer support in the webOS is suitable for detecting basic movement of the phone for interface rotation, but that's about it.