1. Play board games! Here's some spooky ideas a la Wired. I can personally testify to the awesomeness that is Arkham Horror but it is also a massively long and complicated game. Not for the light of gamer heart.
2. Watch scary movies! This is nerdy because it involves you being a little to a lot antisocial. I recommend The Alien Trilogy. Or, you know, whatever's on AMC FearFest because that shiz is bomb.
3. Read scary books! My pick is Something Wicked This Way Comes by Ray Bradbury. It takes place around Halloween and is CREEEEPPYYYYY. And also awesome.
4. Play scary video games! If you're a big video game scare wimp (like me), I recommend Amnesia. It's legit scary but isn't super spendy. Also you can play with the lights on and only get as freaked out as you want to be.
5. Watch the X-Files! It's sci-fi! It's creepy! It has David Duchovny being crazy smart and snarky! It has Gillian Anderson being badass! All of the episodes are wonderful - alien story arch or no.
Do you have any other nerdy ideas? DO SHARE.