I just picked up my second Ranco Electronic Temperature Controller (ETC-111000). I bought the first soon after I started brewing, to brew my first lager. Last year it was installed in my keezer, which means fermentation temperatures have been mostly uncontrolled (which has an impact on final taste). So, we have a small freezer we are not using, which I have commondeered as a fermentation chamber.
These are great devices that can be used for cool or hot temp control, and are relatively inexpensive on Amazon if you choose to wire it yourself (below is a YouTube tutorial I followed). In my case, I cut and stripped an extension chord, which worked great.
Fermentation temps are very important, as the yeast you use will give an optimal range at which the yeast stay healthy and active. As your wort begins to ferment, the temperature may rise as much as 10 degrees above ambient room temperature. Outside the optimal range, you can get off flavored that affect your final product.
If you have an extra freezer/fridge – or can get a cheap one off CraigsList – I would highly recommend getting a Ranco to manage your temperature!