The Design Guide Site

This very "Under construction" page lists design guideline suggestions backed by logical reasoning that has often been proven in usability studies. Many GUI designers either ignore or don't know about many of these basic rules that should probably be common sense. 

Human-Computer User Interfaces in General

Smartphone Graphic User Interfaces

Speech User Interfaces

There was a time when speech based user interfaces on mobile phones and computers were getting to be almost usable. Progress was kind of rebooted when iOS and Android became popular and things took a step backwards