I found this product somewhere on the internet and finally picked some up recently. Last night I cleaned some rust stains in our white porcelain kitchen sink. It got those rust stains up, and all of the other marks and discolorations I've been trying to get rid of.
Bar Keepers Friend is officially my new favorite cleaner! I got mine at World Market, but they probably sell is at better grocery stores and I think at Bed, Bath & Beyond.