Javascript.is(Sexy)
jQuery Cycle Plugin slideshow plugin that supports many different types of transition effects
jQuery Waypoints makes it easy to execute a function whenever you scroll to an element
Parallax.js reacts to the orientation of a smart device, offsetting layers depending on their depth within a scene. If no gyroscope or motion detection hardware is available, parallax.js uses the position of the cursor instead
skrollr sweet scroll detection and controls
grunt is not weird and hard Introducing the grunt task runner
RequireJS is a JavaScript file and module loader
GSAP is a suite of tools for scripted, high-performance HTML5 animations that work in all major browsers
Sizzle A pure-JavaScript CSS selector engine designed to be easily dropped in to a host library
Hammer A javascript library for multi-touch gestures
Video.js The open source HTML5 video player
jQuery Ketchup Plugin Tasty Form Validation
jScrollPane cross browser styleable scrollbars with jQuery and CSS

The Grid System. The ultimate resource in grid systems, and a great example of a responsive, non-fluid, grid design
Grid Based Designs. A directory of grid based design examples
Five simple steps to designing grid systems, by Mark Boulton
Gridness. A blog about grid design
Fluid Grids by Ethan Marcotte
Responsive Web Design by Ethan Marcotte, with an available workshop

Intro to CSS Transitions. A simple tutorial
Blueprint CSS framework. A solid foundation to build on top of, with an easy-to-use grid, sensible typography, useful plugins, and even a stylesheet for printing. Not responsive
960 Grid System streamlines web development workflow by providing commonly used dimensions, based on a width of 960 pixels. Not responsive
Using CSS flexible boxes
Golden Grid System A folding grid for responsive design, and an explanation by Sean Goresht
Fluid Grids by Ethan Marcotte
unsemantic Responsive fluid grid system
Responsive Grid System Easy Responsive Design
The Semantic Grid System
Frameless Grid. Adapt column by column, not pixel by pixel. Non-fluid responsive design