GNUstep GNUstep: A GNU project to write a completely OpenStep compatible programming environment based on Objective-C, with intentions to also maintain Mac OS X compatibility. (Compilers and Environments) http://www.gnustep.org/
ActiveDeveloper ActiveDeveloper: Interactive runtime Objective-C IDE for Windows, Mac OS X, OpenStep NIS. (Compilers and Environments) http://www.interactive-technology.com/
Portable Object Compiler Portable Object Compiler: A preprocessor that will convert Objective-C into regular C. (Compilers and Environments) http://users.pandora.be/stes/compiler.html
OpenStep Specification OpenStep Specification: A copy of NeXT Computer's OpenStep Specification. This is the specification that both Cocoa and GNUstep are based on. (Compilers and Environments) http://www.gnustep.org/resources/OpenStepSpec/OpenStepSpec.html
gnome-objc gnome-objc: CVS home of Objective-C bindings for Gtk+, GNOME. (Compilers and Environments) http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-objc
The MiscKit Frameworks The MiscKit Frameworks: A free collection of Objective-C objects useful to Rhapsody, OPENSTEP, GNUstep, and NeXTSTEP programmers. (Compilers and Environments) http://www.misckit.com/
Cocoa Cocoa: Apple's Objective-C based programming environment for Mac OS X. (Compilers and Environments) http://developer.apple.com/cocoa/index.html