For me, I am a total baking geek. I could talk about the different types of icing, how to pipe, and what the difference in extract and oil flavoring is. I baked 4 dozen sugar cookies this weekend, and just finished icing them for my DD Birthday tomorrow (she will be 2!)
Running and weightloss. Both of those things pretty much consume my every thought. I try really hard to keep it inside most of the time. Oh, and Disney stuff.
I picked up running, and strength training this year. Not a geek about it, but do really enjoy it.
Animals in general, but particularly birds and dinosaurs. Legit. I also geek out quite a bit about all the different forms of art and gardening.
You and my dh could get along, he geeks out on dino. His major in college started as archaeologist, before switching to computer. He knows all the names, and entertains our son with random, info on any dino we see.
Science, data, politics, statistics... I have been known to look up statistics data on Friday nights when having philosophical discussions with our friends to see who is right. I love the internet for that!
And speaking of geeking out... My city is having an election today. The city website posts results as they come in on their website... In a format that can be easily copied in Excel. So I can run statistics as data comes in. It's awesome .