Powell's actually started in Chicago, but we've got the city block bookstore now. In addition to the main store and a couple other smaller stores throughout town, they have a store devoted just to cooking and gardening. It's about the size of a B Dalton or Waldenbooks, maybe a little bigger. 80% or more is cooking. It's mixed new and used.
They also have a clearance counter that's fabulous, but even that clearance counter doesn't have all the clearance cookbooks. It's not the usual crap you see on sale at Borders or Barnes & Noble. (There are currently 252 books in the cooking clearance section.)
Samples of books currently on clearance (these were at the bookstore this weekend when I went in):
Bayless, Mexico One Plate at a Time ($13)
Ripert & Ruhlman, A Return to Cooking ($20)
Martinez, Zarela's Veracruz ($13)
Hazan, Cucina Marcella ($16)
Petrini, Slow Food ($10)
Here's the link:
http://www.powells.com/salebooks/CookingandFood.1.html