Next time you're watching your favorite movie, close your eyes and just listen. Don't pay attention to the dialogue, just the sound effects.
You'll be surprised at how well you can follow what's happening on screen with just your ears. That's because great movies immerse you in the story using quality sound design.
If you don't use sound effects in your videos or presentations, you should start! Sound Jay is a great place to find high-quality, royalty-free sound effects.
You'll be able to download anything from crowd noise to laser beams in both WAV and MP3 formats. You can use them in personal or commercial projects for free, but you can't repost the sound effects online. You're not allowed to sell them either.
Note: On the SoundJay page is an ad for a pack containing "3000 sound effects." The free sound effects categories are below this ad.