A mixin for SASS that uses background sizing to help you create icons from a sprite.

icon-sprite-mixin

@mixin icon($index, $size) {
    line-height: 1;
    vertical-align: middle;

    &:before {
        // Manually define the icon set */
        $columns: 5; // Number of icons going across
        background-image: url(icons/large/sprite.png);
        background-size: $columns * 100%;

        // Size icon will be displayed */
        width: #{$size}px;
        height: #{$size}px;

        // Position background-image based on number of icons in sprite */
        background-position: #{(100/($columns - 1)*($index - 1))}% 0;   

        // Set position to inline */
        content: "";
        margin-right: #{$size/4}px; 
        display: inline-block;
        line-height: #{$size}px;
        vertical-align: middle;
    }
}