My wife recently found a great sale on cereal at a local grocery store... It turns out that she saved our family just under $600.
The store was Price Choppers. It was for 3 boxes of Post cereal for $5. It worked out to be almost 3 for the price of 1.
She purchased 180 boxes ($300 worth!) and was very strangely looked at for purchasing such a large amount (even had to get store manager approval for such a large purchase).
She admits being embarrassed buying such a large amount but weighed the embarrassment against the savings we'd have in the long run. It turns out that she saved our family just under $600. My family of 7 (5 daughters) have cereal for breakfast everyday (and I go for cereal if there isn't anything ready to eat :) ). So we average 1 to 3 days for a single box of cereal - depending on what kind it is. This stash of cereal will last us 6 to 7 months - and at huge savings!
But wait, it gets better. My wife's very smart about this kinda thing. She then reduced our budget entries for future groceries for the next 6 months by $20 less on our large purchase weeks (which is bi-weekly). So our budget went down by $300 for the next 6 months of groceries (spent upfront now); but in reality we now have that other $300 of savings that she will use towards other sales to create more savings or meet other domestic needs. So rather than saving the money and then overspending on that week's groceries on junk food, she's kind of "investing" the money for more bulk savings. She's also cleverly found a way to convert some of these cereals into munchies :), which will probably reduce our junk food spending also!
For major staples in the house - like cereal, crackers, freezies :) - it is worth looking out for these sales.
And, of course, it pays to have a smart and frugal spouse!