For instance, Great Value white bread sold at Walmart is manufactured by Sara Lee. Canned peaches come from Dole, etc.
This also applies to many of the Kirkland brand products found at Costco (Kirkland batteries are made by Duracell, and so on).
It should be noted that often times the generic products are identical or extremely similar to their name brand counterparts, but this is not always the case. As far as I know, the only arena of goods where generics are expectedly 100% (in regards to active ingredients) equivalent to name brands is pharmaceuticals, as law requires them to be.