During development of iPhone Applications, you collect a bunch of helpful code fragments. Thanks to Objective C's nature it is possible to keep those fragments structured. My own collection is available here. Additionally, i keep them in a github repository:
http://github.com/mkernel/iphone-snippets

List of Snippets

• NSArray (SortArray)
  This addition adds an initializer to NSArray which generates an array containing a single NSSortDescriptor object. Very useful when it comes to core data.
• NSSortDescriptor (Initializer)
  This adds a static initializer to reduce the alloc/init/autorelease lines.
• NSString (ApplicationDirectory)
  Adds an initializer which returns a String containing the Documents Directory for the current application.
• NSString (KeychainAdditions)
  Adds a few functions to interface the Keychain using NSString. Supports Keychain's internet account data type and allows to query, add and delete those accounts.
• NSData (Base64Conversion)
  Adds functions to convert a binary stream to it's Base64 Counterpart and vice versa.

This package is from April 1st, 2010: snippets.zip