I'm putting together a resource list of spoken word/literary reading events in and around Portland. I will announce more as I get the website set up and have a clearer vision of where I'm going with this. (I did purchase a domain name last night, which I'm also keeping secret until I know better the structure of what I'm doing!)
In my research, I ran across Colored Pencils, which presents Art and Culture Nights, which includes open mic. I have seen a couple of announcements for these - but have never been. Here is one video from their website to whet your appetite!