We use an electric blanket (twin size blanket on queen size bed)under a feather bed on one of our beds. Before we had the feather bed, we had it under a regular mattress pad. It is actually under a mattress pad, under the feather blanket.
Dd's twin sized bed has a fitted heated mattress pad on it. I cannot remember where I bought it, but it is about 5 years old and still works well.