The articles are written by Luke Wroblewski http://www.linkedin.com/in/lukew
It gives great insights into the importance of desiging sign up forms for mobile apps and how to avoid potential users to drop out just after downloading the app, and actually never use it. One reason for the drop out can be: badly designed sign up forms.
Mobile Sign up Forms MUST DIE
Gradual Engagement for Sign Up Forms
Find plenty of other great tutorials on netmagazine.com for different topics from Photoshop to mobile app development.
A great collection of tools to be used in a design process for complex systems. Some of them are well known and often used typically when designing IT system, like use cases or blueprints. But on this platform you will find many others. Just browse through this great collection and get some inspiration for the next time when you need to solve complex situation with customers
Three parts series (maybe more will follow) about optimizing mobile websites from the google conversion blog Germany (in german language). It gives great hints and guidelines what to take into account when creating mobile websites.
Designing buttons for mobile websites:
Very interesting article claiming usability guidelines for gestural interfaces like touch screens. Unless establishing such guidelines, two steps are taken backwards in usability.