Human Machine Interface Expert

ANDROID DESIGN GUIDELINES

Cocoa Controls - custom UI Component Database for iOS and Mac OS X

Mobile UI Patterns

pttrns - iOS UI Patterns

lovely ui - a collection on mobile ui elements, mobile patterns and more

Modal and Modeless Windows Best Practices

MULTISCREEN EXPERIENCE – Prinzipien und Muster für das Informationsmanagement in der Digitalen Gesellschaft (Beta)

HOW TO: Get Started on Posterous

42 Beautiful Monochrome PSD Icons – Monochromatic Icon Set

Google+ Leitfaden

Android 2.3.4 GUI