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
Huge selection of user uploaded sound effects, licensed under Creative Commons Licenses. https://freesound.org/
Make music using the free-to-use audio and video materials from the Library of Congress
This site offers both free (CC licensed) and royalty free (pay once for use right) music.
Tool for analyzing on-line videos. Allow you to step through animation / video frame by frame. Works with most YouTube and Vimeo videos.