If you take Wildwood rd from ARB in Verona, then turn left on 2nd, then an immediate right onto Shannon, take it to the end, that's 2 miles of uphill. I did it by accident once. Well, I did the first half mile by accident, and walked the rest. It definitely peters out at the end into stuff that may be downhill, or maybe it's just so much easier it just feels like it. You could top out a few blocks west of there, just before 380. I don't know the height difference, but it's basically river to top of Penn Hills.
The Coal Hollow rd mentioned - it's mostly flat until Sandy creek, at least I thought it was. It gets worse at the end, though, making it mean. You could also ride that intersection inbound on Verona Rd, to Frankstown (but west, rather than to Frankstown south... I love Pittsburgh), and it's 1.6 miles and a steadier climb.
Why not just do laps on Mt. Washington? It's not my cup of tea, but the rewarding view from the top almost makes it worth it. None of these other climbs have anything to compare.
Oh, like bj said, Guys Run from Freeport to Fox Chapel rd (maybe a little farther, I recall that hill lasting way longer than I thought polite) is about 3 miles of "up". Really easy to get to, too, just out ARB or Freeport or a mix of the two. The scenery is more attractive there, too.