I have two that I go to frequently.

One is Center Cycle in Renton, WA: http://www.centercycle.com/

The other is Bicycles West, with 3 locations in the Seattle area: http://bicycleswest.com/

Both have treated me very well. I purchased my bike from Center Cycle, but I've gotten lots of good advice, help, and equipment from the Bicycles West in Burien.