Please feel free to share any thoughts on your favorite tools in the comment area.

References: User Interface Guidelines (Official Documentation)

• Android: User Interface Guidelines
• iPhone: Human Interface Guidelines
• iPad: Human Interface Guidelines
• Palm Pre: User Interface Guidelines

Prototyping / Wireframing

iPhone Stencil Kit

Quickly sketch out iPhone UI prototypes. Brainstorm your application ideas using stainless steel stencil and mechanical pencil.

iPad Stencil Kit

Use iPad Stencil Kit to quickly mock-up application ideas for the Apple iPad. How can you refine the user experience? What type of interaction is going to make the app compelling? Let this iPad Stencil Kit help you answer these questions.

LiveView (for iPhone)

LiveView is a specialized remote screen viewing application intended as a tool to help designers create graphics for mobile applications.

iPhonePrototype

DroidDraw

GUI Templates

Android GUI

Android GUI PSD is inspired by idea of teehan+lax and is not intented to be used for final implementation. You can use Android GUI PSD for all of your projects for free and without any restrictions.

1. Android GUI PSD v1.0 by Pavel Matcheck

2. Android GUI PSD v2.0 by Vladimir Grishin

3. Android GUI PSD by Chris Brummel

iPhone GUI

1. iPhone GUI PSD by Teehan+Lax

2. iPhone Mockup Toolkit (CS4) by Meta*spark

3. iPhone Stencil for OmniGraffle by Patrick Crowley

4. iPhone PSD Vector Kit by Renee Rist

5. iPhone GUI PSD by FreshBooks

6. iPhone Interface PSD by 320480

iPad GUI

iPad GUI PSD by Teehan+Lax

Palm Pre GUI

Palm Pre GUI PSD by Teehan+Lax

Emulators

MobiOne (for iPhone / Palm Pre)

Project Ares (for Pal Pre)

Full UI Design Suites

MIDS (Mobile Interface Design System)

MIDS is the first complex dedicated system for automation of UI design, prototyping, and usability testing that meets standard process requirements of cellular operators, handset manufacturers, content and service providers.