InterApp Communication

Contains the URL schemes needed to open other apps from your app.

http://www.handleopenurl.com/

Making your app compliant to the URL schemes

http://iphonedevelopertips.com/cocoa/launching-your-own-application-via-a-custom-url-scheme.html

Some really nice links to get some 

Iphone Designs

Good learnings for designing Iphone page
http://flyosity.com/

Tutorial: Detecting When A User Blows Into The Micby Dan Grigsby on August 19, 2009 · 16 commentsQuite useful  in many of the games and could be fun thing to have in the app. Cool  down the coffee.
Receive input into from the mic and evaluate the sound level and  respond using say give out variable responses based on the input.

17 Best Augmented Reality iPhone Applications (Dec 09)Augmented reality is one of the most exciting technologies around. If you have watched some of those modern Hollywood movies, you have probably seen how our world would look like 20-30 years from now. 


20 Creative Apps For Your iPhoneWe all know that the iPhone does a lot more than just call your friends. As an application platform, the iPhone has been embraced by developers in a massive way, and there are apps that can help you do everything from learning to cook to watching live TV.


Use URL schemes for Iphonehttp://wiki.akosma.com/IPhone_URL_Schemes
Quite useful collection of info you need to make  when calling an external app. like mail, sms ,telephone facebook,etc.