Is there an online site to compare grocery store prices?

[M]

I don't know about the items that aren't on sale, but do you do SouthernSavers.com? This site has all the deals for the three stores you mentioned, all in one place, plus it's a coupon aggregator site where you can find links to coupons from Coupons.com, Smart Source.com, RedPlum.com, and the CouponNetwork by Catalina. (Coupons.com only works with Vista, not Windows 7) There is a searchable coupon database so you can look for coupons for specific items, and there are links to outside coupons like those on Facebook and those on manufacturer's sites. You can sign up for the daily deals email (no spam) to see all the deals for stores in your area.
There are also notifications of deals at other sites and stores, like office supply stores, drug stores, and apparel stores like Coldwater Creek, etc. and online merchants as well. I like SouthernSavers because all the deals are in one spot so you don't have to go searching all over the place for the best deals.