Here's a collection of sites where you can get sound effects and ambience for your projects!
https://freesound.org/ Freesound is a great resource for royalty free and copyright free sounds. Each sound comes with a creative commons license, some of which require credit, so make sure to check those!
https://www.sounds-resource.com/ Sounds resource is an archive of sounds from various video games and PC games, so while they can't be used for anything commercial, you may be able to use them for things like videos or fan games.
https://www.humblebundle.com/software Humble bundle regularly hosts fundraiser bundles of software and game design assets, including sound effects and ambience. You can also put money from your purchase forward the bundles charity. Sadly, humble bundle also puts out bundles of AI books, though, so it's up to you if you think the good outweighs the bad here.
Unreal Marketplace If your project is an Unreal Engine 4/5 game, check out what the Unreal marketplace has to offer! They offer both free and paid sound effect packs for your games. Some you can download as wav files without Unreal Engine installed, as well!
https://pixabay.com/sound-effects/ Another nice resource of free and royalty free sound effects! Attribution is not required, but appreciated!
https://www.youtube.com/ Youtube can be a great place to find copyright free/royalty free sounds too! To get the sounds form the videos, you can use a tool such as mediahuman's youtube-to-mp3 converter.
https://www.gamedevmarket.net/category/audio/sound-fx A paid store where you can find all sorts of sounds and ambience for your video game projects! Humble bundle seems to do bundles with them pretty often so you may want to look into that to save some money here, too.
https://sonniss.com/gameaudiogdc An archive of free and copyright free sound effect packs from the Game Developers Conference! A new pack seems to be added every year, too. :)
https://getsoundly.com/ Soundly is a program more than website, but I have tried it myself and you can get free sound effects from it, and you can get additional sounds if you pay for the pro version as well.
https://www.boomlibrary.com/ While this sound effect site is primarily a paid one, you can get a free monthly bundle of sound effects if you subscribe to their mailing list!
https://blipsounds.com/community-library/ Another great library of free sounds from the Blip Studios community!
https://www.zapsplat.com/ They require you to make an account before downloading anything, but this is another site with lots of free sound effects for your projects!
Itch Io Itch Io is another great resource for both free and paid sound effects!
