Every year, one of my favorite parts of Bumbershoot is Flatstock. I nearly died of happiness when I saw this Carissa's Weird poster from their CD release show in 2001 at Graceland. The whole festival was great, but I think that was one of the first few shows I ever saw in Seattle, and finding this artifact from it for only $20 would have been enough to make this year's Bumbershoot worthwhile.
I also found a nice Sufjan Stevens poster and one for the Arcade Fire's show at the Paramount last year. And no, I don't really have room for any of these.