…I have a tengwar tattoo (for nine, natch) on my wrist.
…I use people’s reactions to this when meeting new friends or dates.
…I couldn’t marry or be in a LTR with someone who didn’t like or know of Tolkien’s work.
…I don’t care about any of this and how it makes me look.
I am using my right hand to type, because in my left hand is a report on various spectroscopic techniques. I was supposed to submit it to one of my lecturers but couldn’t resist swinging by the computer lab* on the way… so here I am.
There aren’t a lot I can add that hasn’t been done, but…
… I have described in detail to my friends why certain molecules are beautiful
… whenever my friend comes into my room he always says, ‘what, working on your ambigram crap again?’ And he’s often right.
… I pepper my speech with so many obscure scientific, SF and fantasy references that people have given up trying to understand me. Even when I’m trying to “dumb down” my speech 
… once got into an argument over the scientific accuracy of certain superpowers. More than once, now that I think about it. Plus, lengthy discussions as to the most plausible methods of gaining superpowers.
… half of my desktop wallpapers come from graphjam. The other half aren’t much better
There are others, but I should submit this report soon. Also, I just remembered I am ten minutes late for a meeting.
*Literally. I tried to just pass through, but the computers were calling me.
…my husband first asked me out over email. (Well, said he was going to ask me out, I guess.)
…I own a Doctor Who t-shirt that no one ever understands.
That is awesome! Pic please. I need to see if it’s casting a shadow on itself.
For my own. . .
First of all, I know what the Utah teapot is.
I created my own language when I was trying to come up with place names for a RPG world.
I’ve been to the World Boardgaming Championships for the last 5 years.
I own 4 Lego Mindstorms sets.
I built my own PVR.
Wrote a database app to create a daily newspaper and player histories for my simulated basketball league.
You do win, I bow down to your superior Galaga skills. I want this one so bad.
…I fully intend to name my first daughter (if such is ever born) after an anime character. (I mean, she already has the same last name as me!)
…I’m a hardcore WoW raider, whcih embarrasses my 13 year old son.
…I met my husband on Usenet
…I have been stalked/harrassed by Kenny Pangborn
…my husband’s first presents to me were not flowers or chocolates, but Neverwinter Nights, Heros 5, and the first five Laurel Hamilton boooks…
…but I don’t read Laurel Hamilton anymore, since she veered to heavily into vampire porn…
…we have greater than 2000 books in the house, most of them fantasy, DnD or other roleplaying games, or references for DnD or other roleplaying games
…I am called the “office nerd” at the office
…I tried to explain WoW to my CEO in terms of “raid leading equals leadership skills”
There’s more…but I feel nerdy enough now.
Cheers,
G
…I have one wall of my bedroom covered with custom made book racks for paperbacks, as well as book cases in other parts of my home.
…I play the accordian and the organ.
…I own a bike helmut with a propeller on the top.
…My glasses currently have tape holding them together (just until tomorrow’s optical appointment, though :)).
Ok… that’s just… sad 
Scrabble as a drinking game… hmmmm
Ok -everyone that has mentioned playing WoW,
IMO, that does NOT make you a nerd. Unfortunately, WoW is so popular these days that it seems like just about everyone is playing.
Now… my daughter is slowly coming out of the Nerd-Closet… she asked for a book on WoW programming!!! Still cant get her to play D&D though.
Oh, and one time I used a D&D example during a job interview, I think in reference to problem solving. The guy was a gamer, but not a D&D’r. The interview pretty much ended after that question and I was hired. Funny thing of it is, my fellow co-workers are all gamers.
I’m gonna take a stab and say that it’s “The Angels Have The Phonebox” from “Blink”.
I’m so nerdy, I almost did a protracted post misinterpreting the OP as saying “I’m so needy”, but then backed down for fear other Dopers would insist my post was actually serious. Do I get a prize?
When I was at school, I bought a cheap microscope so I could determine if sperm really did have little moustaches as crudely depicted in biro in the biology textbook.
Wow, my nerd cred kinda sucks. I’m so nerdy that I belong to several “Sims” forums and I have a website/yahoo group where people can download content I’ve modified for the game.
I’m feeling deeply out of my league here, but …
… I can’t watch Independence Day without mentally keeping count of all the allusions and passing references to other SF works which the film is littered with.
… most of my computers are named after other computers (Landru, M5, HAL9000, Ziggy).
… the one that isn’t is named Albus.
… I stood up in a room full of people and asked Brad Dourif a question I originally asked here on the Dope.
… I DVR NPR.
FWIW, I don’t play WoW and couldn’t possibly care less about it, despite two consecutive girlfriends who were/are big into it.
I’m so nerdy I know who Brad Dourif is. He’s Saavedro.
I’m so nerdy I read my brother-in-law’s Masters Thesis from MIT on using Finite Element Analysis to Determine the Propogation of Cracks in a Planar Surface (my wife stopped me right there, saying that was nerdy enough), and laughed out loud at the subtle joke he inserted. Something about being dismayed when the static analysis of an object suddenly becomes dynamic.
I hate it when that happens.
Well, I know he was also Grima Wormtongue, Peter de Vries, Hazel Motes, and the voice of Chucky. Cuz I’m so nerdy I make lists.
Playing WoW doesn’t get much nerd cred. Modifying it does.
If your daughter isn’t already a computer programmer, get her Hacking World of Warcraft first. World of Warcraft Programming would be tougher for a complete newbie to creating software. The “hacking” book does include writing mods, but it walks through all of the UI fundamentals first, introduces macros, suggests other people’s mods to load and examine, and so on.
… I call myself an Otaku. In my username.
… I don’t merely know who Loki is, but I’ve read many of the surviving eddas.
… I love seeing people freak out when I explain that Loki is normally male - but also Sliepnir’s mother. (It’s just a really, really great pucker expression. Esp. if one is talking to someone who isn’t comfortable with anyone who isn’t hetero.)
… I have GMed an RPG below sea level. (Well, below the waterline, at least.)
… I know enough Gilbert and Sullivan to sing many of the songs, and have even made a few filk versions.
… I have committed fanfic.