Audacity is a powerful open source audio editing program, with many high quality filters you an use to process you audio and make it sound exactly how you want it.
Available for Mac, PC and Linux
Audacity: Audio Editing and Recording
Category: Resources
BBC Sound Effects
The BBC Sound Effects Archive is available for personal, educational or research purposes. There are over 33,000 clips from across the world from the past 100 years.
dig.ccmixter.org
Mostly Creative Commons licensed music, including: Instrumental Music for Film & Video (“Find that perfect soundtrack or theme music for your film or video project.”) A lot of tracks, good search (or find) functionality. http://dig.ccmixter.org/
GIMP: 2D Image Editing
GIMP, the GNU Image Manipulation Program, is an excellent tool for editing images with many features comparable to Adobe Photoshop. It has been around for 25 years and is free and open source. Download: https://www.gimp.org/
Krita: 2D Painting & Animation
Krita is a professional free and open source painting program. It is an excellent tool for concept art texture and matte painters illustrations and comics In addition, is supports 2D animation Get Krita The software can be downloaded from Krita.org
OpenToonz: 2D Animation
Free and Open Source yet professionally powerful 2D animation software. Simulates a cell based animation approach, handles bit bitmap and vector layers.
Meshroom: Photogrammertry
Meshroom is a free, open-source 3D Reconstruction Software based on the AliceVision framework
This powerful photogrammertry tool is available for Windows and Linux
Normal Map Online
This site lets you create normal maps based on images or a height map NormalMap-Online
Poly Haven (Textures, HDRI’s & Models)
Here are two sites with CC0 (public domain) licensed images, one with textures (including bump, normal, roughness, etc) and one with High Dynamic Range Images (HDRI) which you can use to light your scenes. PolyHaven (F.K.A. HDRI Haven & Texture Haven) which also have Models for download
Freesound.org
Huge selection of user uploaded sound effects, licensed under Creative Commons Licenses. https://freesound.org/