The Roadhouse was a bar that served as a central location in Season 2 of the series. It was originally owned by Bill Harvelle, and later operated by his wife Ellen Harvelle and her daughter, Jo Harvelle, and was a safe haven for hunters of all varieties.
It was first seen when Sam and Dean go to a call from Ellen and go investigate the place. When they arrived they were attacked by Ellen and Jo Harvelle. The bar served as a regular regrouping station for the Winchester brothers, where they picked up cases to work from Ellen and visit with the Harvelles and the other primary resident of the Roadhouse, Ash, who was technologically savvy and helped the Winchesters on a number of jobs when requested.
Unfortunately, the Roadhouse was destroyed in an attack by Azazel's minions after Ash discovered the truth of the Devil's Gate and its relation to Sam's disappearance near the end of Season 2. Though it was burned to the ground (resulting in Ash's death alongside all others inside at the time), Ellen and Jo miraculously were not there when Azazel's cohorts destroyed it. It is later seen once again in Ash's representation of Heaven in Season 5's Dark Side of the Moon, which reveals that Ash was happiest in life at the Roadhouse, and that he will now reside there for eternity in Heaven.