“Computer cooling” is the broad term used to describe mechanisms to keep your laptop cool, including your CPU. This generally works not by adding something cold into the mix, but by dissipating the heat. more efficiently.
A passive mechanism for doing so is by using heat sinks. While the design of heatsinks can be quite complicated, the basic concept is to maximize the surface area of the laptop through which excess heat will be dissipated. For CPUs in particular, this often means placing it near the corner of a laptop and by creating ridged ventilation patterns on the adjacent surface. Allowing air to simply circulate through the laptop does wonders for internal temperature.
Making sure that air circulation is maintained around the laptop case is also important. Placing the laptop on surfaces that won't wick the heat away is a bad idea. There are many products available to help you along with this, such as cooling pads for laptops, or you can simply have a DIY approach and elevate the laptop slightly in the air using objects from around the house.
Another method, albeit a more active one, is to include a fan in the laptop casing near the CPU. While this might be a bit noisy and ruin a zen moment or two, it's highly effective, and usually only kicks into place when passive methods just aren't good enough.
Of course, both the fan and the heatsink needs to be cleaned on a regular basis to remove any built up dust, which may in turn cause overheating. This can be done yourself, with a little mechanical know how and a bit of common sense, or by a professional.
Just minimizing your CPU usage can also minimize the amount of heat generated. That doesn't mean you have to stop playing processor-intensive games, just that you might want to poke around for some software specifically designed to streamline and control CPU usage.
The design of the CPU itself is always being improved for greater energy efficiency, which in turn decreases the amount of heat. Some creative heatsinks are also being dreamed up, such as this patent for heating of the LCD screen using excess heat from the CPU.