There is a lot of talk of this newly revived product known as permeable or pervious concrete which is a very usefull as well as a functional product.

In real simple terms Pervious concrete is concrete that allows for the flow through of liquid. It has hollows and tunnel for water, rain, melting snow etc to pass through while still providing a functional surface to walk, drive on and use.

For a great reference and more detailed information click Pervious or porous concrete pavement.