We have a baby foam mattress (52 x 27 x 4 inches) that we no longer need and are thus offering for $10. It is clean and, because it is a foam mattress, hygienic (cannot be infested by dust mites, not to speak of bugs etc.). It is in great shape and as firm as a baby mattress ought to be.

You can pick it up in Menlo Park, close to Santa Cruz Avenue.