You probably heard this term before the 3Rs of waste management strategy 'reduce, reuse, recycle.' The Metropolitan Washington Council of Governments has a searchable online database for reuse and recycle construction material. (you can also download the recycling guide here -pdf).
According to MWCOG, most construction and demolition (C&D) materials are reusable or recyclable. These are things like metals, concrete, bricks, asphalt, untreated wood, cardboard, appliances, fixtures, carpet, and more.
Furthermore, by recycling, it actually helps buildings earn 'green' certification.
Projects that recycle 50% of their waste can earn 1 point. A 75% recycling rate can earn a second point. An innovation credit point is available for projects achieving 90%+ recycling. To earn construction waste management points, projects must develop a construction waste management plan, identify recycling goals, and quantify waste generated and recycled either by volume or by weight.
[via MWCOG]
I think you can also purchase some of the construction materials from stores listed in the directory. For example, there are stores (here and here) that sell antiques and architectural salvage items, i.e. pre-1960 doors, bathtubs, stained glass, etc.
