Amazon offers the Contigo 20-oz. West Loop Autoseal Mug in Stainless Steel for $12.32 with free shipping. That's tied with the per-unit price from our October mention (which was for two mugs) and at least $7 less than you'd spend at a local retail store. It purports to keep liquids hot for up to seven hours or cold for up to 18 hours and features a push-button top.

Update: The price has increased to $12.53.