Here's a DIY project for you this Halloween — a pumpkin with glowing LED eyes that will light up automatically when it gets dark. The idea of rigging some circuit board inside of a pumpkin may be a little daunting to you, but it's really not all that hard.
The core of the project is the light-sensing circuit. It takes quite a bit of natural light to get its sensor to turn off the lighs, so you won't want it in the shade or else they'll always be on — which is a shame, no hiding creepy pumpkins. You'll need some simple components to get it together: a phototransistor so the circuit can sense light, some batteries to power it, LEDs and some other components. Learning how to toss these components together would definitely help you understand the basics of circuitry, and create a holiday decoration to boot.
Head on over to Evil Mad Scientist if you want to give your porch some spunk this Halloween.
CORRECTION: The lights turn off during the day — sorry for the typo. Thanks, Chad!