Also, the NW section of 6speedonline is pretty active. More things happen with that crew than just about any other group in the NW.
I think Exotics and Redmond Town Center is worth mentioning as well. It isn't a group per se, but it is a gathering of Exotic cars every Saturday at the Redmond Town Center. All cars are welcome, especially Lotus. The focus is High-end Exotics.