Your list may vary of course. But here are some things I usually keep a regular stock of, and where to get them cheapest (please correct me if you have any tips):

-Cereal - Jewel, Dominicks - If you're not picky, sales bring them as low as $2 a box.
-Cheese - Jewel, Dominicks - They usually have 2 for 1 sales on blocks of cheese. Go for the blocks, the convenience of having it pre-sliced is personally something I can do without.
-Couscous - Technically the cheapest would be to get the loose grains at Whole Foods or somewhere that sells it that way. The boxed variety Near East often goes on sale at Jewel/Dominicks.
-Hummus - Trader Joe's, Harvestime, Stanley's - I usually make it, but if I'm lazy or wanting a bigger selection, these places have the small-size containers for $2-3 usually, versus more than $5 as I recall the last time I bought it at Dominicks or Jewel.
-Sandwich bread - This depends on your individual taste really, but in general, this is another thing you can save on - and better yet, get higher quality - if you're willing to sacrifice the convenience of pre-sliced. Go to the bakery section instead of the bread aisle. Otherwise, Trader Joe's has some tasty varieties of pre-sliced bread.
-Soy milk - Whole Foods, Trader Joe's - One of the few things that tends to be cheaper at these places at regular price.. usually not more than $2 for a 1-qt non-refrigerated carton. West Soy is usually cheapest.

I will add to this list as I think of more...