Cool Borders is a really small CSS library which can be used to add gradient based border flair to your website.
It's inspired by the explanation class at the bottom of the CSS Tricks article Web History Chapter 2: Browsers. Cool Borders uses the same approach to create effects with a variety of starting points and directions.
There two types of effects - corners and three sided. All effects are created using two classes; the base class cool-border and another which denotes the gradient direction (three sided effects) or if it's a corner effect, and the origin corner. The following code sample shows the syntax possibilities of the second class: cool-border-{h/v/corner}-{top/bottom}-{left/right}.
Examples can be found here.