They often post in the above group, but in case you don't find them sooner:
Eastside Smash (ESS) holds Sunday weeklies in Bellevue. $5 entry, $5 PM bracket. PM singles bracket is always held first, and then afterwards there's usually a free bracket that people decide on the spot - PM doubles (standard), PM all-star (hasn't happened in a while), or Melee singles (I think they've done this, not sure). There's always at least a few Melee setups for those interested, and if there aren't you can just ask since there's usually way more PM setups than necessary for bracket.
GameClucks holds Monday weeklies in Lynnwood. They always hold Melee/PM/S4 singles, and rotate which is the main event each week. I know there's also at least a few players here that have some interest in RoA, if that interests you. $3 entry, $5 main event.
UW Smash Club holds Tuesday weeklies in Seattle. Melee singles bracket, PM Singles bracket, Melee doubles bracket, and another I forget are on rotation, but there'll always be at least a few Melee/PM setups I think. Melee singles is $1 for bracket (no entry fee), all others are free.
ePeen Gaming holds Thursday weeklies in Renton. PM singles every week, and Melee/S4 singles brackets on rotation. $6 for either event, so entry is free if you're just going for friendlies. Or as their event descriptions always list it, "$4 Melee/Sm4sh/PM singles," and "$2 entry fee per event."
EDIT: Also make sure to also join
PNW PM,
PNW S4, and
PNW RoA if you're into them.