• 25c3: The Ultimate Commodore 64 Talk (YouTube) - By Michael Steil
• All about your C64/1541/1581 - By Ninja/Dreams
• No More Secrets V0.98 - By groepaz
• 65xx opcodes - By Graham/Oxyron
• VIC Article - The mighty… By Christian Bauer.
• The SID homepage - By Mr. SID
• 6502.org - About the 6502 CPU (almost identical to the 6510 in the C64).
• The Fridge - Source code, tools and technical information for Commodore and 6502 programmers.
• Project 64 - The most comprehensive source for Commodore Computer manuals on the internet. Includes “Programmers reference guide” and “Mapping the C64”.
• C64 graphic modes - Description of C64 graphic modes
• VIC-II Color Analysis - All you ever wanted to know about the colors of the commodore 64 by pepto
• International C64-Wiki-Project - All about the C64
• German Version of C64-Wiki-Project - All about the C64 (German Version)
• Replay Resources - Everything about c64/c128 tool cartridges you could be interested in.
• C= Hacking magazine - Available online. Contains huge amounts of useful articles.
• disC=overy magazine - Similar to the C=Hacking magazine, but fewer issues were released of this one.
• Atari Magazines - Some info on 6502 programming hidden there
• docs on Arnold FTP - Texts on various C=-related topics.
• 6502 killer hacks at AtariAge forums
• Commodore Knowledge Base - maintained by Cameron Kaiser
• Ruud's Commodore Site - specifications related to Commodore hardware, with very useful in-depth docs on Commodore drives, including GCR encoding. - Maintained by Ruud Baltissen
• The visual 6502 - A quite cool dynamic visualization of the 6502 as it executes various opcodes.
• 6510 Assembly Instructions Cheat Sheet - PDF for printing. Includes cycles, opcodes and illegals.

• Biggest C64 Machine Language etc tutorial (10,8MB) - Links directly to binary!
• Dustlayer - 6502 tutorial by actraiser
• Covert bitops rants - By Cadaver. Contains all kinds of useful coding tutorials
• 64bites - Video tutorials by Michal Taszycki
• A$$EMBLE IT - C64Assembly code tutorial on creating fun things like games, picture displayers with scrolling message and music. Run by Richard Bayliss
• An Introduction to Programming C-64 Demos - By Puterman/FLT.
• Learning ML for the 6502 Series - by Craig Taylor
• Pagetable blog - A bunch of C64/6581 tutorials, tricks, and articles
• Project J - A 100 step tutorial to a full game - by Georg Rottensteiner

• CSDb coding forum - Any kind of c64 coding related issues. Maintained by Perff/NoName.
• retrohackers.com - About Retro Replay related development. The forum also has a lot of useful files and sourcecodes uploaded in one of the subs. Maintained by RaveGuru/Instinct (outdated).

• Open Source C64 Demos - Thread at CSDb
• 1bir (1 Block Interactive Raycaster) - by Wisdom/Crescent (CSDb)
• Artefacts - by Krill/Plush (CSDb)
• 69 Positions - by Raf/Vulture Design (CSDb)
• Motivation 2 - by Oxidy/Fairlight (CSDb)
• RADWAR Speech Synth Sourcecode - by MWS/Radwar (CSDb)
• SP0256 Speech Emulation - by Streetuff/TRSI (CSDb)
• S:T Lars 2007 Sourcecode - by JackAsser/Instinct (CSDb)
• C64+1541/71 turboloaders - by KM/Taboo
• Mahoney BitLive4 demo source - By Mahoney (CSDB)
• Source Code & Tools - Some Source Code & Pc Tools

• Turbo Assembler — Reference document to Bacchus version of Turbo Assembler 5.2
• Turbo Assembler Homepage - maintained by Style. Also featuring Turbo Macro Pro.
• Turbo Action ROM V1 - Action Replay ROM file for the Retro Replay which includes a version of Turbo Assembler that runs from the internal RAM of the RR. Hack by SounDemon/Dekadence.

Don't link directly to binaries in cases where a proper homepage for the assembler is available.

• CA65 and CC65 - Assembler/c compiler/Linker
• Kick Assembler - by Slammer/Camelot. Assembler with extensive Java-style scripting. Runs anywhere with Java.
• ACME - Cross assembler with a lot of nice features, without being bloated. Includes macro support.
• Dreamass - by Doc Bacardi/The Dreams
• WLA DX - by Wille Helin. Supports many processors, including 6502/6510 and 65816.
• 64TASS Old TASS by KM/Taboo updated by Soci/Singular
• TMPx - Cross assembler that is source compatible with Turbo Macro Pro
• k2asm Open-source cross assembler with linker, scopes and python-macros
• XA (xa65) xa assembler / disassembler by Cameron Kaiser and others.
• DASM Official home of the DASM cross-assembler.
• C64 Studio, open source IDE specialized for C64 game programming.

These are tools that can be used to transfer code that has been assembled on a PC/Mac and execute it on the C64 without forcing the user to store the contents on a C64 disk first.

• Final replay and Codenet - by Graham/Oxyron. Requires a Retro Replay cartridge with RR-net.
• RR.exe - by Groepaz/Hitmen. Requires a Retro Replay cartridge with SilverSurfer.

Although a lot of tools are available on CSDb, there are also a number of tools on the list maintained by Fairlight that are not available on CSDb.

• CSDb - A lot of tools (both for C64 and cross dev).
• Fairlight Tool list - List of tools (both for C64 and cross dev).