Links related to developing on/for Amiga

Reference Material and manuals

AmigaDevHelp Large collection of AmigaOS3 (and before) documentation including a large number of examples.
Guide to Amiga Compatible Programming
Natami/Amiga developer docs HTML versions of the official AmigaOS manuals from Commodore as well as the hardware reference manual and a guide to the m68k instruction set.
Amiga Developer Docs - Another source for the official AmigaOS manuals
AROS Wiki Book User guide for AROS, which contains a significant section on developing for AROS. The “porting” section has relevant information for updating old Amiga software to more recent AmigaOS3 or 4 setups as well (information on differences between SAS/C and gcc, most of which applies to vbcc too, in particular)
Documentation of the AMOS file formats - AMOS is a BASIC style language for the Amiga with extensive graphics and sound support; this documentation is most interesting for people who wish to manipulate source code written in AMOS in external tools.
Amigan's Abandonware page has some Amiga manuals/books.
Amiga File Formats Lists specs, utilities etc. for accessing Amiga file formats.

Peter Hutchison's Amiga C Tutorial
Amiga OS4 Programming Guide Project to create a set of tutorials on C programming for AmigaOS4.
An Introduction to AMIGA Programming Using C by Michael Ness Covers up to and including AmigaOS4.
Amiga C Kurs fuer Einsteiger German programming tutorial for Amiga
How To Code V7 Extensive tutorial / e-book on Amiga development
Writing a compiler Chris Gray's tutorial for writing a compiler for the Amiga (for a language called “Toy” designed for the tutorial) in Draco.
ARexx Tutorial Chris Patterson's two part ARexx tutorial.

Aminet is a good source for programs including source code. The list below is intended to cover non-Aminet sources only:

Amiga Software by Paul Kienitz
Dice C Compiler For m68k. Compiler is probably outdated for most use today, but source might be interesting.
Reverse engineered Amiga "Cracktros"
Blog entry w/source links (Aminet and Github) for "Banker"
Source code and Youtube videos for demos by Triumph
YAM - Yet Another Mailer Major example of a current Amiga app that's portable to the various AmigaOS-like OS's.
Assembly source for Protracker
Some Amiga Basic programs
Sceptre of Shalimar AmigaBasic game w/source
Various AMOS sourcecode Including spatial sound.
AMOS sourcecode for Midi Companion, W-Lib and others as well as disk mags.
Amigan Software Software releases from Amigan Software, most with source.
Source code for ACE basic compiler
Source code for Frexx editor
Amiga C Source Repository
Amiga Open Source List of Amiga open source projects, specifically projects with no or outdated AROS versions.
Asm Pro Assembler IDE
AWeb Source for th AWeb web browser
Testaware Amiga projects A selection of Amiga Basic, AMOS, AMOSPro and asm games and tools, including source.
comp.sources.amiga archive Link to the earliest Google Groups archived messages of comp.sources.amiga (now defunkt)
HD-Rec Major music app written using AmiBlitz3
CU Amiga C Tutorial source code

Amiga ports including gcc and ixemul and lots more.
Page tracking effort to port OOo4Kids to AmigaOS4 contains an outsider view of getting started, including some solutions and links to external resources.
Ktadd's Amiga OS4 Development Hotlist
Amiga Coding Wiki
Michael Sinz' Enforcer page Enforcer is a MMU tool for the classic Amigas to identify memory related bugs - this page has the source code; For current use Muforce may be a better alternative.
Commented disassembly of Kickstart 1.3 and a variety of other old Amiga system software.
Assembler page Bunch of assembly resources, mainly for “classic” 68k AmigaOS
Vasm A highly portable and retargetable assembler that also supports Amiga
Tags in PCQ German article on using taglists in PCQ (pascal compiler)
JForth Now freeware Forth compiler for Amiga
pForth Public domain portable ANS Forth written in C w/source.
M2Amiga Now open source version of the M2Amiga Modula 2 compiler
Aztec Museum Mostly of historic interest. Archive of old Aztec C compilers, including the Amiga version.