I've had really good luck finding staples at the 99 Cents Only store. My sister turned me on to the fact that they sell food, including produce. They always have different things, so I can't really plan for what I'll buy there. I usually go there first to see what staples I can get for a cheaper price than the grocery store
This week I got:
Butterball Turkey Lunchmeat
5 lb. bag of potatoes
A dozen eggs (I bought 2)
A big package of green onions
Everything was $1, except for the green onions, which were $0.25.
I had an awesome find of half-pints of blueberries the last time I went. They don't have any limit on how many you can buy. Nothing is out of date--I think they just get overstock, because you never know what you'll find the day you go in.