Well let's see here.
1. I've seen every episode of StarGate SG-1 and StarGate Atlantis.
2. I've read encyclopediaesque articles on every StarTrek species.
3. I have read more Sci-Fi books than I can count.
4. I can fluently speak technobabble.
5. I have a Klingon to English dictionary.
6. I study quantum physics in my spare time.
7. I've seen every ST: Voyager episode.
Wow, now that I read that, I feel so geekish.

Add:
1. and just about every cheesy 80's sci-fi series ever made
2. and encyclopedias of Star Wars, and other series
3. ditto, but I've even played the Roleplaying Games based on them
4. Yep, and a smattering of Klingon
5. Yep, and an Elvish dictionary, and Drow dictionary
6. Me too, especially anything with String Theory or M Theory
8. extend that to the other ST franchises...
and:
I've got the Star Wars toys...
Not only have I played D&D, I've been a DM (and for other RP games)
I used to run a guild on EQ
I dress up and go to Ren Fests, and I even dress up for Fantasy/Sci-Fi movies on occassion.
I have a 4.0 GPA in college...(that's pretty geeky)
Though I could have pre-ordered the book, I'll be in line at midnight tonight to get the new Harry Potter book...just to meet the fans of the
books.
Collection of UFO books, films, posters, even a copy of the Roswell Record front page from July 8, 1947.
I married someone almost just as geeky as I am...
That's pretty damn geeky folks...
EDIT: and I try to go to DragonCon each year, and a couple of local Cons.
[edit on 20-7-2007 by Gazrok]