The link takes you to a zip file on dropbox that allows you to download about 200 MBs of wireframing and Mockup kits
Apple Design Site
Apple Human Interface Guidelines
Get in-depth information and UI resources for designing great apps that integrate seamlessly with Apple platforms.
Google Material Design
Material Design is a unified system that combines theory, resources, and tools for crafting digital experiences.
Material Design Guidelines
We challenged ourselves to create a visual language for our users that synthesizes the classic principles of good design with the innovation and possibility of technology and science. This is material design. This spec is a living document that will be updated as we continue to develop the tenets and specifics of material design.
Everything you need to know about conducting useful user interviews
Creating products based on your own needs is easy – if you’re building something just for yourself, you don’t need to talk to anyone else because you know what you want.
It’s pretty unlikely that you’ll ever design a product for yourself. If you want to make a product that will be used by other people, it’s essential to talk to them to discover their wants, needs and, experiences.