While I've enjoyed the flexibility and goodness of CSS Preprocessor like LESS for a long time, I discovered that many webmasters don't know about it yet.

LESS CSS allow you to extend CSS capabilities with programming features such as Variables, Functions or Mixin, and Operation which will enable you to build modular, scalable, and more manageable CSS styles.

Here is what it looks like:

.gradient (@color1, @color2) {
background: linear-gradient(top, @color1, @color2);
}
@color1: #0078bd;
.class1 {
    background-color: @color1;
    .class2 {
        background-color: #fff;
        color: @color1;
    }
}

As you can see you can:
* Declare and use variables.
* You can nest rules.
* You can declare and use functions.
* And so much more.

There are also built in functions: Lets say you have a color and you want another shade of that same color, You can just do

 darken(color, 5%)

or

lighten(color, 5%)

.

All these allow for maximum code reuse, modularity and scalability.

Check http://viewslog.com/discussion/329/ if you want to learn more about LESS. I covered the basics of less with example codes to get you started right away.