Oh, yeah, there’s that.
Eyewear. Seventeen+ years as a dispensing optician. I can get you into a pair of glasses that you’ll like, unless of course you truly hate glasses. In that case I can talk to you about Refractive Surgery. And I could teach you quite a bit about contact lenses, too. (disclaimer: I am NOT certified for contact lenses, but I do hold American Board of Opticianry Certification, neither of which is required in PA). I do NOT refract or fit contact lenses. I do all the stuff after you’re done with the doctor. And I like it 
Wanna know the symptoms of retinal detachment?
Things I know more about than most people:
Whitewater kayaking. I do OK for a flatlander.
Fender electric guitars, particularly Stratocasters. I don’t play very well but I read a lot about them and I’m pretty good at identifying, assembling and setting them up.
Reptiles, particularly snakes.
Old Italian switchblades.
Fairly knowledgeable about guns.
Fishing - primarily freshwater, specifically walleyes.
Damn. That’s a short list.
Um, walking in stilettos.
Minesweeper.
I know a lot about carpeting. Luckily, this is actually necessary for my job so I’m not a complete loser.
A little bit about birds, a little bit about beer, and a crapload about European history and art history, mostly pre-1800.
An expert on two genera of plants, human anatomy and biology in general.
Pretty good on watch history/repair.
Darn good chili maker, biscuit baker, and beer brewer and gardening.
Close to expert on health matters.
Think I’m an expert on politics and investments. Not everyone agrees, starting with my family.
UI design & usability (mostly enterprise apps–I don’t really do consumer software)
Technical writing
Old science fiction, fantasy, & horror (by no means an expert, but I know more than your average man-on-the-street)
Cocktails (ditto)
A decade ago, I could have put “virtual reality” on the list.
Crap, what have I got to offer… I’m a journalist, so I’ve got a solid working knowledge of that business, First Amendment law and some history. I know plenty about blues, the music of the '60s and '70s, tennis, the Marx Brothers and the Simpsons.
Expert, hmmmm
Stamp Collecting.
Cooking. Still looking for the ultimate Kung Pao chicken recipe though.
Bible. If I don’t know the answer, I know lots of people who do. No one is an expert in all of it.
Epistemology. See Bible. I love this subject as it satifies my intellectual need to know why people believe what they do and how they come about to those beliefs.
Kicking conspiracy theory ass. I will always be a skeptic and to logical for my own good.
semi-expert in dogs
old people and old people diseases
prof. believe none of what you hear and half of what you see.
Animal behavior & dog training
knitting, spinning & dyeing w/ a teensy bit of that specific niche internet e-commerce
maybe a little bit of San Diego, whippets and greyhounds, alternative fuels & happiness in being in the moment.
Medieval English literature (esp. Chaucer).
Disney (esp. animation and Disneyland).
Coming up with conspiracy theroies
Programming
Getting 1000 KOs in Dynasty Warriors V
I am an expert in carbon nanotube membranes having done extensive research in this area. The group I worked with discovered high speed flow through carbon nanotubes. Wikipedia included the discovery in its timeline of the history of the nanotube.
I know more than quite a bit about metals and alloys, plastics, semiconductors, and chemistry and physics since I am about to complete a degree in materials engineering but am no expert in any one of those areas IMO.
Areas of non-expertise, but very thorough knowledge and worth mentioning:
-sitar
-music theory
-architecture
-photography (I have photo’d nearly 80 weddings)
Me too! Also, spelling. I’m always pissed off that these, my best
skills, seem to be of such little importance to the rabble.
Customer service/dealing with people. It’s odd, really, because people
frequently annoy me and if I had my way I’d be shut up alone with a
book, but since I do have to cope with people, I’ve gotten damn good at
it.
I memorize phone numbers, a very useful skill in this day of faxes and cells and homes and offices. Everyone seems to have about 20 different numbers.
I’m always on time and I type very fast and accurately because I learned on a manual typewriter.
I don’t get along with adults at all, but I relate to children really well.
I am the (self-appointed) world’s leading authority on the subject of military codewords (Just Cause and all that).
Good cook, a darn good English teacher.
Ice Cream–especially its history.
Homebrewing beer.
World Capitals.
A lot comes down to how you define “expert.” Are we meaning “in my circle” or “region/nation/world-class”?