Amazon Warehouse Deals offers the used Frigidaire 5,000 BTU Window Air Conditioner, model no. FRA052XT7, for $53.55 with free shipping. That's $32 below our July mention of a new unit and the lowest total price we could find by $86 for a new model today. This air conditioner features a 2-speed fan, antibacterial filter, and adjustable thermostat.

Note: No warranty applies, although it's covered by Amazon's return policy.

Update: The price has increased to $56.53 with free shipping.