If you need a quick same day run (leave 9am back by 2 pm), try IAD - SHD (Staunton, VA - 90 miles from IAD).
The fare is $86.00 with only a 3 day advance purchase (United Express).
You will even have a view of the of the Shenendoah mountains through the front of the aircraft. Neat if you can be seated in first class section - seat 1b.