I would add checking out kplu.org our local News and All That Jazz radio station's web site. Especially peruse the calendar section - lots of live music every night in Seattle, and much of it jazz. KPLU is also nationally recognized as one of the best jazz stations in the country, and they live stream the show so it is listenable outside radio transmitter range. 88.5 if in Seattle.
If you have time, also check out my home town Bainbridge Island, a pleasant 35 minute ferry ride from the downtown ferry terminal.