Powell's:
the fabulous Portland bookstore - go there in person if you can, but
otherwise, their web site is a good alternative (particularly for used
books)
Amazon.com:
I worked there for years, and they have great selection and good prices
Abebooks.com: good source for used
and out-of-print books
Jessica's Biscuit: excellent site
for discounted cookbooks (and not just old or remaindered ones, either)