Some of the more interesting ones in alphabetical order (up to about 50-75 miles from Pittsburgh) - Private unless stated. You had better have good contacts to get on a number of these (don't ask me):
Allegheny - Ross did a lot of it. Short front 8, long back 10 one of my favorites in the area
Birdsfoot - Public, fun, a little hilly
Butler - Very walkable and enjoyable
Cedarbrook - good public, 36 holes
Chartiers - 9 holes by Willie Park, 9 more
Chestnut Ridge - Tom's Run - good public also another 18 there
Churchill Valley - Held a US Women's Open in 1959 Short these days, but fun
Cranberry Highlands - new fun muni
Diamond Run - Gary Player design, hilly - lots of housing
Edgewood - Good old Ross
Fox Chapel - Raynor, wonderful - Golfweek top 100 #2 after Oakmont in my opinion
Green Oaks- Another good Ross
Hannastown - my home course, contact me if you want to play, hopefully I can join you.
Indiana - Willie Park did the first 9, updated and some holes gone, but still good
Latrobe - Arnie's home
Laurel Valley - Arnie's second home GW Top 100, Dick Wilson originally
Longue Vue - Interesting, hilly but fun
Montour Heights - Dye (Pete and PB I believe) hilly, near airport
Nemacolin - Tillinghast - fun, not quite up to New Castle, but good
Nemacolin Woodlands - Mystic Rock - Dye, 84 Lumber classic site - very upscale resort
Nevillewood - Nicklaus some very good holes
New Castle - Tillinghast - best of his around here bar Sunnehanna, tough greens
North Park - fun muni
Oak Tree - good semi-private
Oakmont - say no more
Olde Stonewall - high end public, interesting routing
Quicksilver - good public, US Open qualifying course, Hooters Tour there, former Senior Tour site
Pittsburgh Field Club - classy, parkland course
St. Clair - good, but undergoing extensive renovation this year
Sewickley - good, hard. Some say it is harder than Oakmont
Links at Spring Church - Enjoyable, wide-open public.
Sunnehanna - Tillinghast, wonderful GW Top 100
Treesdale - Palmer, 27 holes - lots of housing
Valley Brook - good 27 hole layout
Westmoreland - good 27 hole layout Joe Lee and Dick Wilson
Williams (Weirton WV) - good old course, shortish but fun Loeffler from Oakmont design
Willowbrook CC (Apollo) - good smaller private course
Jay, Gettysburg is nearly 200 miles from Pittsburgh.