Portland is one of the best places to live cheaply! When I lived there, I enjoyed its very active Freecycle community, as well as the general culture there of leaving crap at the curb. Yard sales are so prevalent that you can go on Craigslist on the garage sale section and search on the exact items you want. Beyond the free or nearly free, I enjoyed:
1. Groceries at Winco--employee owned, so cheap.
2. Food samples at New Seasons--lots of freebies. Not great for shopping, but the Hot Wok setup is nice. You fill your own bowl with whatever you like for a fixed price. Then they prepare it with sauces, noodles, and such.
3. The bins. Goodwill is not so cheap in Portland, I found, but the Goodwill bins are cheaper. Dirtier, though.
4. Baby/kids stuff: Just 4 Kids consignment/used shop in Hollywood.
5. In addition to faboo Powell's there is Title Wave. Stunningly cheap books sold at deep discount by Portland's unbeatable library system.
6. Chinook Book: If you are in it for a little longer, this is one of those discount books with cheapo tix to theater and such. It's only worth it if you are staying longer or if you split it with your hosts so they can use it thereafter.
7. The Alibi: Tiki Bar with no cover karaoke!
8. ReBuilding Center: Do you get excited by abandoned fixtures and reclaimed tile? I sure do. This is the place to score it.
9. Super cheap second run movies at the various McMenamins locations--Kennedy School was my personal favorite.
Enjoy PDX!