This is part of the Illustrator CS6 Lesson Plan.

3.5 Demonstrate knowledge of how to work with brushes, symbols, graphic styles, and patterns.

Brushes
Ultimate Brush Guide
Creating Custom Brushes
Master post of brush tutorials

Symbols
Symbol Basics
Symbols Simple
Symbol Tools Video
Using Symbols Video

Graphic Styles
Appearance Panel Video
Graphic Styles Basics
Using Graphic Styles
Appearance Panel and Graphics Styles Basics

Patterns
Ultimate Pattern Guide
Simple Patterns Video
Creating repeatable pattern for the web video
Geometric Patterns