Raster and vector image creation and editing

• Krita - "a professional FREE and open source painting program". This is what I use for drawing digitally. Very nice selection of brushes.
• GIMP - Often hailed as The Free & Open Source Image Editor, as the site itself states. My hatred and frustrations directed at program cannot be understated, but it deserves a place here nonetheless.
• Photopea - One of the best-known alternatives to Photoshop, only getting more and more popular as Adobe dives deeper and deeper into anti-consumer practices with each year passing.
• Aseprite - Probably the best-known program for drawing pixel art; nothing else that I know of can match it. Not free, but it is open-source! You just have to compile it yourself.
• Inkscape - The only vector graphics program on this list, mainly because I've never had the need for any vector graphics.

3D modelling

As far as I'm concerned, there is only one free (and open-source!) program that can stand anywhere in the viscinity of industry standard giants like Maya, Autodesk, and Adobe. Meet the myth, the legend, the creation of hundreds of contributors...

• Blender - nothing else compares.

That being said, Blender lacks a little in the texturing department. It's acceptable, but one might have to look elsewhere for textures...

Textures/Materials - ready-made texture maps applied to 3D models

• Poly Haven - All these materials are under the CC0 license. Commendable!
• ambientCG - Quite a small website, but all these assets are also under CC0. Donate if you can!
• Open Texture Library? - An even smaller site, born after textures.com got too greedy in early 2024. They don't even deserve a hyperlink.
• CG Bookcase - another small site. I like all the variations on similiar textures.

People often forget about audio. Music is the best way to make someone feel something, and sound effect are essential for better interactivity. USE THEM!

Music creation - nowadays plenty of people use DAWs.

I think this section requires some clarification. There are many DAWs out there, but what works best for you may not work for others. FLStudio seems to be the industry standard, but it is not a requirement to get into music creation. Honestly, just pick something and try it out! You will never get anywhere if you're stuck trying to pick "the best" program. As Ville Kallio so eloquently put it...

• LMMS
• Reaper
• Cakewalk
• SoundBridge
• BeepBox - small site
• Bosca Ceoil - a simple program for beginners

Sound creation

Sometimes it's best to create the sounds you need yourself. You can just record yourself banging some pans together, eating an apple, or you can make the sound with your throat. But sometimes you need a program to make sounds for you.

• Chiptone - The most sophisticated, evolved program on this sublist. Nice UI, plenty of control over the sound.
• Bfxr - One of the programs Chiptone is based on.
• sfxr - The grandfather of many sound-making programs, including the ones listed above.

Ready-made sounds and music

But audio can be a lot of work. Why not rely on other people sometimes?

• FreeSound.org - A large sound library, which anyone may contribute to, Make sure to check each sound's specific license before use!
• Designing Sound's SFX Libraries list - An old, unupdated list of independend sound effect libraries.
• Kevin MacLeod's Incompetech - Hundreds of pieces by a legendary creator. You've already heard his music, though you may not realize it.
• Steven O'Brien - not quite as notorious as Kevin MacLeod, but he's made plenty of music.
• MUSOPEN - a library of royalty free renditions of well-known classical pieces. Very useful, many performances you can find online are copyrighted.
• Free Music Archive - Another big archive. Check each piece's license before you use it!