I'm looking for a comprehensive list of all tools for debugging iPhone apps, and any online resources relating to them.
How about the tools that come with Xcode, like gdb and Instruments?
This will also help: http://google.com/search?q=how+to+debug+iphone+apps
I assume this questions is about Xcode debugging. However i am developing web based iPhone apps using the like IUI and iWebkit etc. Normally for web development i would use Firefox/Firebug but for iPhone the Webkit is better (IMHO) and the javascript debugging is excellent. I also use the iPhone simulator rather then needing to deploy the code to a server.
I've incorporated the following tools into my Xcode pipeline:
GHUnit - Unit testing which can run on the simulator and devices, and allows debugging.
OCMock - Mocking framework for use in the unit tests.
Appledoc - For creating more apple like API docs and including them into XCode.