Via Seahawks Insider:

Sep 9 Tampa Bay 1:15pm
Sep 16 @Arizona 1:05pm
Sep 23 Cincinnati 1:05pm
Sep 30 @San Francisco 1:05pm
Oct 7 @Pittsburgh 10:00am
Oct 14 New Orleans 5:15pm (Sunday night)
Oct 21 St. Louis 1:15pm
Week 8 BYE
Nov 4 @Cleveland 1:05pm
Nov 12 San Francisco 5:30pm (Monday night)
Nov 18 Chicago 5:15pm (Sunday night)
Nov 25 @St. Louis 10:00am
Dec 2 @Philadelphia 10:00am
Dec 9 Arizona 1:05pm
Dec 16 @Carolina 10:00am
Dec 23 Baltimore 1:15pm
Dec 30 @Atlanta 10:00am

Here's a more readable NFL version.

And here's the complete NFL schedule.

UPDATE: Changed the times to West Coast time.

Preseason game dates are (mostly) TBA:

Aug. 12 at San Diego 5:00 p.m. (NBC)
Week 2 (Aug. 16-20) at Green Bay
Week 3 (Aug. 23-27) Minnesota
Week 4 (Aug. 31-Sept. 2) Oakland