Here are some of my favorite geeky pumpkins with links to where I saw them. Once you're inspired, at the bottom of the list you find some more links to carving templates and even more galleries of amazing carvings.
The Lantern Corps - a nice collection of pumpkins and squash to make up a complementary set. Click the link and browse the artist's gallery to see how cool they look when they are all aglow.
Cthulhu - I like when the pumpkin is carved and sculpted all at the same time!
Voldemort - This one really creeps me out.
Greedo - Greedo is overlooked too often, but this guy got it right. Do yourself a favor and check out that link. He does amazing things with pumpkins. There are dozens of carvings/sculptures to look at.
Evil Dead movie poster - You give Ash love, you give me love. This family carves pumpkins every year and all of them are archived on their site.
Serenity - You can't take the sky or the pumpkin from him. Again, this artist has a lot of great carvings. I guess pumpkin carving must be addicting?
Free Pumpking Carving Templates
Spooky Sith-o-Lanterns from StarWars.com
Pumpkin carving templates from Pink Raygun - Ghostbusters, Dr. Who, the Hunger Games, zombies, and more
ThinkGeek's Pumpkin Template Contest - 48 templates including Buffy, Cthulhus, robots