Backcountry ski club?

I live in the Seattle area and am interested in joining a local randonee/ ski mountaineering club. What options are there?

Here are two:
Washington Ski Touring Club
Mountaineers (Foothills Branch)

You already have!

Next winter I'll be forming a new club. The "No Sweat - Low Adrenaline" back country ski club. It will have bylaws dictating a 2000' vert daily max, a mandatory 2 hour transition that will include lunch with mild adult beverages and no yo-yo's over 300'. Keep checking back.

Sounds like you may have an opportunity to start one.  You could call it the Treehug Ski Club.  : 

There is however a solid AT/Tele crew on TAY, if you frequent the site and manage to rally with others you will find there is a great group of folks here.

I think Tayer's are mostly non club types that's why we are here, but there are some whom teach for the mounties bc skiing and ski mountaineering for what it's worth.

It has a rather broad interest base, but the Cascade Cross Country Skiing Meetup Group
www.meetup.com/The-Cascade-Cross-Country-Skiing-Meetup-Group/
has a good percentage of BC trips on a fairly regular basis.