DogFriendly.com
www.dogfriendly.com
On this site you can find an extensive list of dog friendly places including hotels, travel information, and dog parks and hikes.  

Explorerdog.com
www.explorerdog.com
This is an excellent place to find some great hikes for dogs, pet-friendly hotels, local events, and more.

Issaquah
Bark Park
Issaquah Highlands
Exit #18 off I-90, North on Highlands Dr., Right onto NE Federal Dr., Right onto NE Park Dr.
Left on 25th Ave NE, Left on Natalie Wy.
The park is on the Right.

Mercer Island
Luther Burbank Park
2040 84th Ave SE
Mercer Island

Redmond
Marymoor Park
6046 West Lake Sammamish Parkway NE

Sammamish
Beaver Lake Off-Leash Open Area
2526 244th Ave SE at Beaver Lake Park
This park also has a special section for smaller dogs.

Seatac
Grandview
37 acres
S 228th St & Military Rd

Seattle
Genessee Park
4316 S. Genessee St.
Seattle, WA

Golden Gardens Park
8498 Seaview PL NW,
Seattle, WA

I-90 Blue Dog Pond
Martin Luther King, Jr. Way and Massachusetts St.
Seattle, WA
The Northwest corner is the off-leash area

Magnuson Park
Large field area and fenced in beach access. This park also has a section for smaller dogs.
6500 Sand Point Way
Seattle, WA

Northacres
I-5 and N 130th
North Seattle , WA
This park is not very big, but it has a great little "mini trail" through it.

Woodland Park
50th and Aurora
Seattle, WA (Greenlake area)