Some parks near-ish Kennywood (all driving times are VERY rough) 
 Conneaut Lake (90 minutes)  
Idlewild (2 hours?  I haven't been there yet actually, although that'll be remedied this weekend)  
Lakemont 
DelGrosso's 
Six Flags Worlds of Adventure 
Waldameer  (all 2 hours in various directions)  
Cedar Point (3)  
Hershey (4)  
Knoebel's (4-5)  
Six Flags America (4)  
SF Darien Lake (4, I think, haven't tried it yet)  
King's Island (5)  
Dorney (5-6)  
King's Dominion (6)  
BGW (7)  
SF Great Adventure (7-8)   
Note that for me driving times don't scale linearly -- a park twice as far away will take a bit more than twice as long to get there since I need to stop and stretch more and more often the longer I'm sitting ;)   
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--Greg  
http://www.pobox.com/~gregleg/
 *** This post was edited by GregLeg on 8/1/2001. ***