Design in Seattle ?  

Stores
Velocity was probably the most popular one but it has sinced closed. There appear to be a number of vintage shops based on google search, but I doubt you will find many deals to be had.
The Seattle Art Museum is pretty nice.
Of course, there is the Space Needle and the Gehry-designed Experience Music Project (which may or may not be your cup of tea).

Besides the legal weed?
Art Deco..Perhaps the old VA hospital/Amazon headquarters and Harborview med center. Not a ton of Art Deco here I don't think - could be wrong.
Second the library idea - fantastic building. Space Needle is fun on a clear day but obviously crowded with tourists.
I'm afraid I'm not much help on the shopping front. Pike's Place is worth the walk through for the flowers alone but it's crowded this time of year.
Canlis is nice for dinner/view/mid-century architecture but it's pricey. Might be worth going to have a drink though.
Edit: Eh...link won't work. Just google Canlis.

I'm in Seattle.
SAM is a...
I'm in Seattle.
SAM is a great couple of hours--lots of nice stuff.
The Ballard locks are fun for an afternoon.
Space Needle is fun, but can be crowded and is touristy.
EMP/SciFi museum are fun to stroll through.
There are often vintage deals to be found at the Sunday morning Fremont market, and the nearby Fremont Vintage mall is worth a stroll.
As for shops--Ten22Home in Fremont is great, and the owner is incredibly nice and knowledgable. Chartreuse in Belltown is also a fun visit. Several good antique malls in town--Pacific Galleries has some MCM, though you'll definitely pay for it.
As for food:
+1 to Canlis for MCM dining at it's finest. Definitely $$$$ though. If you're into food more than ambience, there are a huge number of great restaurants that have opened up in the last few years, specializing in NW cuisine. Fish is really what we're best at. 😀

Seattle-
My favorite Seattle day:
Breakfast- at Lola's, on 4th. Get the pancakes, house made sausage and a side of hashbrowns.
Stroll the market, graze. Get sausages at Uli's and browse DeLaurenti. Spicy Mocha at Dilettante. Browse the westlake / 5th Ave area
Dinner- How to Cook a Wolf, Queen Anne
Seattle Architecture Foundation has info and walking tours.
...and yes we have, weed, gay marrige, and Macklemore!

Seattle Art Museum sounds OK
Seattle Art Museum sounds OK. We are going to do touristy stuff. Thankx.

Ah, a foodie
Design aside, food is where I live. Maria and I will definitely get into the eating scene. Mmmm.

GREAT !!
You might have made our evening.
Confirms my opinion that Seattle is not a MCM place. Can't remember any Art Deco. Funny, why not? NYC is so Art Deco. Love La Guardia. Even the French love it - and the hate us.
Space Needle - BTDT - 40 years ago. But Canlis sounds nice to impress the lady.

Perhaps not MCM
But there is a lot of contemporary modern design going on in Seattle.

Like oysters?
The Walrus and the Carpenter.

Woody ...
I kinda think I know where you are coming from. WHOSEZ I don' dig musik?
Thanks. My lady and I might look into the music scene.

Keep it comin
There is a lot of good stuff coming in that I will check out. Given Seattle is not the MCM capitol of the world, I can entertain myself with food and music.
But from the responce, I am guessing that most of U are East Coasters !!! OR you are not Microsoft groupies 🙂

i live in seattle and looked...
i live in seattle and looked over what others have said, so here's my 2 cents:
1. Architecture: art deco not so much but certainly some examples. PacMed was mentioned and this towers over beacon hill. you can't miss it from the I-5 corridor. other art deco includes a few hospitals in the central district as well as buildings around pioneer square like seattle tower & exchange building. to me, downtown is a real mashup of architectural styles and it's not difficult to get around by foot between pike place and pioneer square. a lot of the public libraries feature great design and the downtown main library is seattle's ode to contemporary design. also as far as the seattle center goes, note the rock and roll museum as well as the sculptural elements both new and old (we just installed a chihuly garden, but if you really want glass, take a side trip to the tacoma glass museum).
2. Food/Coffee: save your money and don't go to canlis, unless you're really into exquisite service and dressing up entirely (totally valid, just not my thing)... i'd skip most (not all) of tom douglas too. ethan stowell is where you want to go for amazing NW/italian fusion with a seafood focus. there are a number of great gastropubs (quinn's is my favorite). i'd recommend focusing on ballard neighborhood or the pike/pine corridor leading into cap hill for some hidden gems. As for coffee, i am a coffee roaster by trade so i'll just say this: if you just love sbux and want to spend your time in seattle with them, i guess you should visit the fake original in pike place. if you're in love with sbux but looking to branch out, stop by monorail espresso downtown - still darker roast but much better and real classy/underground and if it's the weekend Costa is your barista. but, if you want some real great amazing, special coffee, check out places like analog, herkimer, vitta, stumptown, 7Roasters, victrola

I'm in Seattle too. No, not...
I'm in Seattle too. No, not a MCM paradise. The best of it is downtown and at the Seattle Center--it's more than just the Space Needle and the monorail. Also, there are a lot of beautiful private homes, and you could explore some of the lovely neighborhoods here by car, assuming you have one.
If you do have a car, a great afternoon trip would be to take the ferry to Bainbridge (fun in itself) and take the short drive to the Bloedel Reserve. It's a beautiful garden that takes less than 2 hours to walk, well worth it, and the Japanese Garden has a MCM guest house by Paul Haden Kirk which is filled with Nakashima furniture.
For art deco, check out the SAM's Japanese Museum in Volunteer Park, very nice building in a beautiful setting. I am not that into art deco but there some nice examples here and there. I think the best buildings are the Talking Library in South Lake Union (moderne style) and the Seattle Tower downtown.
There are a lot of great restaurants here. I second Walrus and Carpenter for oysters, if you like them, although the wait can be ridiculous. I would probably avoid Tom Douglas and Ethan Stowell restaurants, you can do better. Bar Sajor in Pioneer Square is beautiful. Speaking of SAM, I think the restaurant there is one of the nicest contemporary dining rooms in the city--have lunch there if you go to the museum. Canlis is beautiful if you want to really splurge.
If you are here for a while, an overnight trip to the San Juan Islands is well worth it.
Enjoy your trip!

Grendel
What is Macklemore?