You can go to http://www.anyleaf.com/grocery-deals and it will give you a good idea of how it works. Use the categories or the stores on the right to narrow things down as well.
They are either screen scraping or have a deal with one of the few major circular systems that are out there. MyWebGrocer has specific terms of service disallowing you to scrape and use the content for example - they also make use of proper robots.txt to prevent (polite) bots. So in terms of Raley's they must have a deal set up... or at least they should.
I am willing to take full blame for this confusion - I didn't know how else to coin these systems.
MyWebGrocer, ShopLocal and one other that escapes me at the moment, are companies that provide Circular (weekly specials that are sent to homes either as inserts with-in newspapers or in special ad bundles) information on the web. From what I can tell there are some exclusivity in between grocery chains and the company that provides online Circular information.
OK, that was my guess though they aren't called that here in AU.
Wonder if the companies cover costs for the chains in exchange for info that they can use in other ways?
Grocery specials and inserts in Australia are nearly always by the stores themselves rather than aggregated. We don't really have grocery coupons either.
They are either screen scraping or have a deal with one of the few major circular systems that are out there. MyWebGrocer has specific terms of service disallowing you to scrape and use the content for example - they also make use of proper robots.txt to prevent (polite) bots. So in terms of Raley's they must have a deal set up... or at least they should.