Useful iPhone SDK articles

http://www.edwardbenson.com/2009/01/10/creating-a-blocking-nag-screen-with-nsuserdefaults/

http://iphoneinaction.manning.com/iphone_in_action/2009/09/core-data-part-4-inserts-updates-deletes.html

http://developer.apple.com/iphone/library/documentation/UIKit/Reference/UITextField_Class/Reference/UITextField.html#//apple_ref/occ/instp/UITextField/leftView

http://regexkit.sourceforge.net/RegexKitLite/

http://forums.macrumors.com/showthread.php?t=473359

http://blogs.oreilly.com/iphone/2009/01/defining-legal-input-character.html

http://stackoverflow.com/questions/433337/iphone-sdk-set-max-character-length-textfield

http://groups.google.com/group/three20/browse_thread/thread/1dc38ac9d7176b77

http://github.com/klazuka/TTRemoteExamples

Also another useful tip:

Also, you can pull up the preferences file in the plist editor if you are running on the simulator. You will find the file in (at least on the Mac):

~/Library/Application Support/iPhone Simulator/Users/Applications//Library/Preferences/.plist

Decompiling:
http://tungchingkai.blogspot.com/2009/02/how-to-decrypt-iphone-ipa-file.html
http://dvlabs.tippingpoint.com/blog/2009/03/06/reverse-engineering-iphone-appstore-binaries

Using zlib:
http://stackoverflow.com/questions/289274/error-when-import-zlib-in-iphone-sdk
http://samuraiblog.com/wordpress/2009/11/02/compressing-nsdata-objects-using-zlib/