An Introduction to CSS3 Transitions - CSS3 . Info
Useful info on CSS Transitions
SVG Gradient Background Maker
Handy
The ultimate CSS tools for web designers | CSSmatic
Gradient generator, border radius, noise and box shadow
gradient-scanner
Handy too to pick up a gradient from an image
Getting Familiar with the Flexible Box Layout Model
Getting Familiar with the Flexible Box Layout Model
CSS3 Generator - By Eric Hoffman & Peter Funk
ProtoFluid - HTML5 and CSS3 Web App Prototyping
Test your @media queries and web app on various screen sizes
CSS3 Please! The Cross-Browser CSS3 Rule Generator
You can edit the underlined values in this css file but don't worry about making sure the corresponding values match, that's all done automagically for you.