There's a great Tumblr that explores various UI Sounds - http://beyondthebeep.tumblr.com/

Also Raised Beaches have a library of UI sounds on GitHub - http://raisedbeaches.com/octave/

We just released a pack of over 500 professional UI sounds for app developers: http://rcptones.com/dev_tones

I actually end up creating all of my sounds from scratch using the OP-1 Digital synthesizer[1]. You could probably generate a good kit using Garage Band if you have a Mac. Just remember: white Keys == happy notes, black keys == sad notes.

Here is a video of me going though some sounds I generated for an iOS game I wrote: http://instagram.com/p/d5hrssSveM/

[1] - http://www.teenageengineering.com/products/op-1

1000+ sounds here - https://icons8.com/sounds/

Thanks for sharing, @Sarah K! I'm the Jordan behind the Beyond The Beep blog :) One of my main goals with the blog is to show how inherently expressive these tiny UI sounds can be. Whether you're designing sounds from scratch or finding them on freesound.org, I hope you won't just drop them into your app because they sound cool.

Try to give the selection of your UI sounds the obsessive care you'd give to picking the color of a logo – the potential to improve the user experience, communicate your brand values, and delight your users can go a really long way with well chosen sounds. Check out Jambox and Skype for my two favorite examples of great UI sound design.

http://www.freesound.org maybe?

Showed my sound designer boyfriend this thread, and he's currently working on a few UI sounds to give away. Keep an eye on wntrjams.com! c:

Loosely related, but http://choir.io is a great implementation/example of UI sounds.

http://unton.es/

After wading through thousands of disparate and fragmented UI sounds, across libraries and collections I felt there could be a better way, and launched Sonify (https://www.sonify.co), a library of sonic identity packs for digital projects.

Packs are cohesive, delivered with 30+ meticulously crafted audio files, engineered to supplement all core user interface interactions.

The first kit is live (with a free sample) with many more are on the way. Please take a look, welcoming all thoughts and feedback for improvement.

Check out this ui sounds https://unisounds.pro/

Check out this sound pack containing organic/real recorded UI sounds. There is also a free Lite version to download and try out: http://www.soundexmachina.com/uisounds-organic

Check it out: http://appsounds.pro

It's several months late, but I recently put out a library of sound effects for UI projects called SoundKit. You can find it here.

http://soundkit.io

Actually resources are pretty well developed. They're catered to game developers and video/special effects. Personally I use

http://soundrangers.com

But there are a ton of other stock sound websites