Construction Junction is a gem. Find gently and not so gently used furniture, building supplies, lighting, and all sorts of other stuff. The warehouse is huge, and if you look, there are some seriously cool treasures here. A giant(I'm talking probably 12' wide) chandelier, a wood-burning stove, 27 tons of sand stone in the parking lot. This is a great place to get cheap building supplies and help out the environment by recycling.
That isn't the best part, though(Well it might be, depending on what you're here for). Construction junction is also home to many other awesome things. Most notably, the space upstairs is aptly named The Space Upstairs - enter from the side into the world of the modern improv dance troupe The Pillow Project( http://www.pillowproject.org/ ). Also, at night this is the location of Pittsburgh's FreeRide ( http://freeridepgh.org/ ) program - a bike information and repair program which encourages people to learn how to fix old bikes to make them new, even offering people a free bike to fix up if they volunteer a certain number of hours. It's also the home of the Steel City Big Pour, a local beer tasting event, and probably a lot more that I don't even know about.
Construction Junction is definitely a treasure trove, and not just for building supplies, but for some of the coolest things in Pittsburgh