Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Mobbin - Latest mobile design patterns & elements library
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.
pttrns - iPhone and iPad user interface patterns
Bubble.io - Building tech is slow and expensive. Bubble is the most powerful no-code platform for creating digital products.
UX Archive Animated - iOS apps animated user flows