I've gotten those too. The letters/emails are carefully worded so the subject screams "Pending domain registration!" to make you think it's your actual domain expiring, but the small print says that the service they offer is "registering" your domain in some random "world business directory". This way it's not an outright scam, in that they do render a (completely useless) service in exchange for your money, but of course they hope that the random admin/manager who sees the "bill" won't realize the difference and will pay up.