+1 to the STC-1000 temp controller. I've built 4 now for $30 a piece (if you already have your own spare power cable). I have mine strapped to a keg / carboy with bungee cords just like Rustym has his in the pictures above. I just use a washcloth folded over a couple times as the insulator rather than foam. This set up allows me to perfectly control my fermenting / lagering / serving temps within 1 degree.
But of course, the chest freezer or upright fridge is sold separately!