Like all animals, chickens need fresh, clean water to survive.  While researching the internet to determine the water solution that was right for me, I came across a plethora of quality products.  Here is a list of the most popular chicken waterer (prices are approximate):

These seem to be the product-of-choice these days.  They attach into just about anything (buckets, plastic bottles, PVC, etc) and most people report that their chickens learn to drink from them almost immediately.  Easy solution to keep water clean and accessible.  Water source can be outside the coop to make for easier filling. There are several types on the market and the choice is really personal preference.

MERSUII Threaded Style
$6/pack of 10
water nipple

Saddle Style
$6/pack of 10
saddle style water nipple

Feeder Cups
$17/pack of 5
nipple feeder cup

Standard waterer that hangs on the side/top of the coop or sits on the ground.  Benefits to a canteen style waterer are price, durability and ease of use. The downside is that they do not hold much water so you often have to place several around the coop.

Galvanized Steel Canteen
$11 ea
hanging canteen

Hanging Waterer 
$13 ea
harris water fountain

Galvanized Double Wall Fountains
$30 2gal size
double wall fountain

These off-the-shelf automatic fountains usually work using a pressurized water line (e.g. garden hose).  A valve will turn off the water once it reaches a certain level.  They do provide a constant flow of fresh water but they are prone to spillage.

Automatic Poultry Waterer
auto poultry waterer