When I first started keeping kosher four years ago, I had a Chabad Rabbi come to my home and help me kasher the kitchen. He told me never to trust a plain "K" as a heksher, since it could mean "kangaroo" for all we know. He did say that the K on Kelloggs cereal was fine. Does anyone know of a list of other plain "K"s that are accepted by the Orthodox or Conservative community? Thanks.