This is a really nifty way to light up your town at night and when the sun rises the lights will turn themselves off. One set of lights will require:

1 Redstone Block


 

4 Glowstone Lamps


 

12 Fence


 

1 Sticky Piston


 

1 Daylight Sensor


 

The Build

The schematic for this is extremely simple. Place 4 Fence Posts with a space in the middle. Build them 3 Fence Posts high and place a Glowstone Lamp on top of each post. Place a Sticky Piston 1 Block high and above the Lamps in the center then a Daylight Sensor on top of the Piston. If its daytime the Piston will extend, go ahead and place a Redstone Block on the extended Piston arm and there you go. Now when the sunsets the Lamps will light your streets.

How it works

When a Daylight Sensor is connected to a Piston and the sun is out the Piston will be extended and vice versa when the sun has set the Piston will retract. So with the Redstone Block stuck to the Sticky Piston and the sun sets the Daylight Sensor activates the piston retracting the Redstone Block up into the center of the Glowstone Lamps giving them power.