Am I Responsive
Preview your site on 4 different viewports (desktop, laptop, tablet, mobile)
Android Design Guide
Official Android design guidelines
Android Patterns
Official Android pattern descriptions
Beautiful Web Type
Showcase of the best typefaces from the Google web fonts directory
Bootstrap
Front-end framework for responsive websites
Call To Idea
Collection of app and web component examples
Color Picker
Fun interactive way of picking colors and creating color palettes
Designspiration
Design inspirations across digital, print, interior, photography and more
Dribbble
Show and tell for designers
Emmet
Chrome extension to find responsive design breakpoints and create views for each
Favicon Generator
Generate multi-platform favicon pictures and HTML
Find Guidelines
Links to official brand guidelines of popular online brands
Font Awesome
Large icon font fully customizable via CSS
Font Squirrel
Free fonts for commercial use
Font Squirrel Web Font Generator
Convert and create fonts for @font-face
Fonts In Use
Archive of typography indexed by typeface, format, and industry
Foundation
Responsive front-end framework
Google Design
Google's entry point to design across all platforms
Google Fonts
636 free to use font families and counting
Google Material
Google's Material design guidelines
Google Material
Google Material color swatches for Illustrator/Photoshop and themes for Illustrator
Google Roboto
Google's Roboto font
Google Typography
Google's typography guidelines
Gratisography
Free high-resolution pictures that can be used on personal or commercial projects
Grid Based
Showcase of grid-based sites
Grid Calculator
Create and download grids for Illustrator or Photoshop
GuideGuide
Photoshop extension to simplify guide and grid creation
IcoMoon App
Create SVG's, PNG's, or custom fonts from 4600+ icons
Information Is Beautiful
Beautiful, interesting and useful visualizations, infographics and diagrams
iOS 7 UI Transition Guide
Official guide for app transitions from iOS 6 to iOS 7
iOS Design Cheat Sheet
Resolutions, icon sizes, element sizes, and typography info for iOS 7
iOS Human Interface Guidelines
Official iOS interface guidelines
Kuler
Create or browse color schemes
Linea
A free outline iconset featuring 730+ Icons
Little Big Details
Collection of the finer details of design
Logoed
(Mostly minimalist/simple) logos
Mapsicons
Country maps in 11 sizes or as SVG
Media Queries
Inspirational websites using media queries and responsive web design
MinimalSites
Showcase of minimalist sites
Mobile Design Pattern Gallery
Flickr collection of mobile design patterns
Modern.IE
Get screenshots of how your site looks on several different browsers and devices
Nice Portfolio
Curated showcase of design portfolios on the web
One Div
Icons in pure CSS and one HTML div
One Page Love
One Page Website Designs
Pttrns
iPhone and iPad user interface patterns
Responsive Patterns
Patterns and modules for responsive designs
Screen Siz.es
Screen specifications of the most popular devices and monitors
Service Design Toolkit
Workshop materials, posters, manuals, and technique cards for service design
Service Design Tools
Communication methods for the design process
siteInspire
Showcase of sites by styles, types and subjects
Stylify Me
Create a quick overview of a site's CSS styles including colors, fonts, sizing and spacing
Swissted
Vintage music show flyers redesigned into international style posters
The Noun Project
Large collection of free and paid-for icons
The Stocks
Several royalty free stock photo options in one place
Typ.io
Curated examples of web font combinations
Type Sample
Identify and sample web fonts via bookmarklet or Chrome extension
Typewolf
Web Typography examples + background and similar font recommendations
UI Animations
User interface animations
UI Faces
Free sample avatars for UI mockups
Unsplash
Free (do whatever you want) hi-resolution photos, 10 new photos every 10 days
Use Your Interface
Transitional interface animations
User Onboarding
Step by step analysis of user onboarding implementations
UX Archive
iOS user flows for different tasks
WhatFont
Chrome extension to identify any web font with a simple click
Windows 8 Templates
Microsoft's assets for Photoshop, Illustrator, Powerpoint, Balsamiq
Windows 8 UX Guidelines
Official Windows 8 UI guidelines (PDF)
Workmark.it
View all installed fonts in your browser