Interesting thing popped up today:
http://www.usa3000.com/commuter/
Lots of short hops from PIT, ORD, PHL, CLE, STL and several others.
Some of the fares are extremely reasonable (PIT - PHL for $49.99) while others are kinda high (PHL-BWI and PIT-CLE for $99.99).
The schedule sucks - but this is still an interesting thing to keep in mind.