IAD Spotting Locations

Does anyone know of any spotting locations for IAD? I plan on making a trip to IAD on my way back from Virginia Beach on August 12. I don't want to spend the $12 to park at the Udvar-Hazy Center, so I'm interested in alternate locations. Keep in mind that I will be coming up from I-95 in the Richmond area, in case you guys want to give me directions to the different spots.

Gotta make it a little even between the military aircraft and the civil aircraft, ya know? I'll be at NAS Oceana shooting Hornets, Super Hornets, and (hopefully!) Tomcats and if time permits, at Langley AFB shooting endless numbers of Eagles and hopefully some Raptors.