Countdown to Halloween: October 26 - Carve a pumpkin
For more advanced designs, check out Evil Mad Scientist Laboratories instructions for creating Cylon and robotic Dalek jack-o-lanterns.
Roy Villafane also has a great tutorial for carving sculptured faces into pumpkins. I suspect it's actually harder than he makes it look.
ETA: My Science Project has tested different methods for keeping a carved pumpkin fresh. Their conclusion: both dilute bleach and the "Pumpkin Fresh" spray work. Read their description for all the gory (well, moldy anyway) details.
Tags: Halloween, pumpkin carving