Macros for Designing by Contract in Objective-C simplifies the process of using the Design by Contract software methodology invented and pushed by Bertrand Meyer. This involves creating a "contract" for each Object in your program that explicitly states the input and output ranges that the Object expects. The macros implement the pre- and post-assertions as well as invariants and references to "old" variables (the state of the variable before entering a method).
NSFileHandleExt is an Objective-C extension (Cocoa/GNUstep) for the NSFileHandle class (which handles files/sockets). This extension provides support for much easier network programming for protocols like HTTP, IRC, telnet, etc. (everything that sends messages in lines suffixed by \n).
Popup is an interactive learning aid for pairs of words. It behaves much like a stack of flashcards, but handles one-to-many and many-to-one word relationships better. It features an editor for cardstack files with support for copying and pasting groups of words, as well as drag and drop. It has two quizzes. One for memorization, and one for spelling practice.