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.