Like Sacrelicious, I've dried lots of nettles for tea.

This year I'm also thinking about trying something like nettle pesto (like the Fat of the Land version or something, http://fat-of-the-land.blogspot.com/2009/03/stinging-nettle-pesto.html ), since it might be a good way to freeze a big amount.

One final method of preserving them that I can think of is pickling. I tried a small amount last year and will probably do a lot more this year. With the first little batch, I simply packed fresh, unblanched leaves into a jar with some kind of flavored vinegar, herbs, salt, and garlic cloves. I forgot about it for months, but when I finally opened it up, they were very good (and didn't sting me!)

Unfortunately I couldn't seem to track down yak butter anywhere, but if you're going to make this happen (and at this point I'd say it's a long shot), my best suggestion is to contact the folks at River Valley Ranch http://www.rivervalleycheese.com/

They're located in Fall City and have been known to sell yak milk mozzarella at Seattle farmers markets. You might be able to buy some yak milk from them, but I'm guessing you would have to churn it yourself...

Beyond that, it looks like if you want something that can be ordered online, pre-made, the best I could find is this Tibetan Yak Cheese -
http://www.kaboodle.com/reviews/tibetan-yak-cheese-8-ounce-by-igourmet.com

I used to order yak cheese soup a lot at the Himalayan Sherpa Restaurant on the Ave. I always wondered where they got the cheese for it. It was my favorite thing on the menu and could still be ordered for a while after it disappeared from the menu, but then unfortunately the restaurant disappeared too.

Or, one other idea is to go for water buffalo butter. It definitely doesn't have the same ring to it, and I can't say whether it's a good substitute for yak butter, but it came to mind after reading this quote from one of the River Valley Ranch owners - "The butterfat content of yak milk is very comparable to water buffalo milk" http://pnwcheese.typepad.com/cheese/2007/10/river-valley-ra.html

It seems to be available here:
http://gourmetlibrary.com/products/52121-Delitia-Buffalo-Milk-Butter

You've Changed by Momus -

Me and her and the ghost of you
You and him and the ghost of me
Two plus one is three and two plus a ghost is three
I guess there must be six of us now
...
It's not love, it's mathematics...

What about Bonal?

I haven't had it myself, but it's "made by infusing gentian root, herbs from the Grande Chartreuse mountains, and cinchona (quinine), in a Mistelle base, producing a wine that is known for its complexity," and check out this local lead from just a week ago -
http://parisgroceryseattle.wordpress.com/

I just got started looking on this side of the state too, and unfortunately I don't have any good tips for places around here yet.

However, for step 2 (positively identifying what you've found before you eat it), the most helpful resource I just learned about is this:
http://www.psms.org/id_clinics.html

You can just walk in on Mondays at the UW Center for Urban Horticulture from 4pm-7pm and people from the Puget Sound Mycological Society will help you identify mushrooms you bring in.

Koji made by Cold Mountain (described on the package as rice kernels covered with a fragrant white bloom of Aspergillus oryzae mold) -- you'll need it for making your homebrew sake!

It's also a very cheap source of white tea. I recommend the big 200g boxes of shou mei white tea by Foojoy ("longevity eyebrow" tea -- sweet, toasty flavor).

In the produce section, it's the only place I know of to buy myōga (sometimes called "Japanese ginger" but with a flavor of its own) in season.