Normally, I'd put the link to the Clog! (seattlecomedyblog.com)'s Open Mic List here, but it seems they haven't updated it since before Giggles became Jiggles...and it's missing more than a few semi-regular open mic and fairly open indy shows.
Here are the biggies:
MONDAY: Comedy Underground, Seattle (Pioneer Square)
50-70 Comics sign up...Carl puts 30-40 of them up...those that get up get 3 minutes of stage time (tightly controlled, you get the light at 2 minutes and you get played off to music if you blow past the light.)
TUESDAY: Laughs Comedy Spot, Kirkland
Around 20 Comics, generally, get stage time. If Dave doesn't know you or if you're new, you're expected to bring 6 customers with you in order to get on the list. The (somewhat) saving grace is that admission is free.
WEDNESDAY: Parlor Live, Bellevue
Haven't been to their open mic...I understand that it doesn't take place in the actual comedy showroom, but in a corner of the pool hall.
There are also, I believe, shows at Pegasus Pizza in Kirkland.
THURSDAY:
Thurst Lounge, Seattle (Ravenna/U-District)
Brett Hamil runs the weekly open mic at this upstairs bar. I had fun the one time I played there for 8 customers and 12 other comics.
Odd Duck Studios, Seattle (Capitol Hill)
Does a late night comedy workshop for stand-up, sketch, improv that is open. Haven't been to it, myself.
FRIDAY:
People's Republic of Koffee, Seattle (Capitol Hill)
The coffee shop run by the guy in charge of the People's Republic of Komedy alt-comedy group hosts a comedy open mic every Friday night in a room that holds 30 people.
Jai Thai Seattle (Capitol Hill)
Haven't been to this one, but I've been told that every other week it is either an Open Mic or a Booked Show.
SATURDAY: No open mics that I know of...
SUNDAY: (most)
Comedy Underground, Seattle
They used to run a showcase night on Sundays, but because so many people were coming for their Monday Open Mic, they changed it to another open mic...most Sunday nights (sometimes, other events pre-empt it.)
I'm sure there are other indy shows that I'm not aware of...and there are open mics down in Tacoma (40 minutes South) as well.