Take an hour once a week and pick up the area in front of and around your home or business and make a difference! If every able-bodied person, young or old, did this each week we would not have a litter issue in McKees Rocks! It's ONE hour, and makes such a huge difference. There's no better time to start than NOW.
Environmental center. Cross between Heinz History Center, The Science Center and the Phipps. Discuss the past and present of Pittsburgh and offer solutions toward a future with cleaner air, water, etc. Different stations in the space could have wildlife learning (birds of the city, flora of Western PA, etc), a greenhouse to grow..."produce"...and could include spaces for the Green Building Alliance, Venture Outdoors and Grow Pittsburgh to have outposts or headquarters. The hope could also be a push toward sustainable energy production. (full disclosure, this was my wife's idea, as she is much smarter than me but didn't have the time to type it up. :) )
How about an indoor park space? A covered space that can be used for festivals, events, and farmers market year round