Washington State is home to magnificent mountains such as Mt. Rainier, evergreen forests such a Olympic National Park; large bodies of both fresh and salt water such as nearby Lake Washington and Puget Sound, the pacific ocean on the coast and home for outdoor retailer REI so one expects the outdoors to be pretty popular here.
Outdoor activities near Seattle are numerous any time of the year. Just 45 minutes east from downtown Seattle you can be at the Snoqualmie Summit Ski Park (mostly beginner to intermediate). Or Seattle is about 100 miles from either Olympic National Park to the west (after taking the Bainbridge Island Ferry from downtown) or 100 miles from Mount Rainier National Park to the south.
Mt. Si is a very popular (and steep) hiking trail and only 30 minutes from downtown. A visit to the breathtaking Snoqualmie Falls is in order on your way to Mt. Si.
One gay group that organizes outdoor activities throughout the year is OutVentures. From hiking to biking, kayaking to backpacking, rafting to scuba diving, rock climbing to skydiving – check their calendar for upcoming events. The group requires a $20 membership ($30 per couple) and is primarily geared towards Seattle area residents.
Ski Buddies is a very popular gay group for winter snow activities.
Seattle has been called the “2nd Best Gay Ocean Sports City To Live” (just behind San Diego)
Of course, for an outdoor enthusiast, no trip to Seattle would be complete without a trip to the REI flagship store.
Triangle Recreation Camp is a gay campground not far from Seattle.
http://www.gayoutdoors.org/ has resources available on a national level.
Team Seattle is geared towards more sports and competitive activities.
Here is a book I recommend, while general in nature, really concentrates on activities nearby or actually in Seattle.