ARRL has a Field Day Station Locator on-line. If you are looking for any station in your state (or province! The Canucks play, too!) you can click a button and scroll down to your state--and find an incomplete list. Whether the "missing" stations are due to the ARRL or clubs dropping the ball, I don't know.
But I can tell you that the Federal Way (WA) Amateur Radio Club is not listed but will be operating WA7FW (and an event station, I think WA7DR?) from Lakota Park in Federal Way.
Note that the "By-state station locator" lists stations by their call signs. If you're looking for a particular club, you need to know their call. Also, this list is supposed to just be "public" stations, not, for example, a city Emergency Coordination Center exercising it's volunteers. (While I did see at least two RACES-type groups listed, they could well be doing a public outreach operation. I happen to know that the Kent Communications Support Team from the City of Kent, WA, will be standing up their ECC, but it will only be open to city employees, it being in a restricted area.)