If you like good beer, one of the area's best microbreweries (with restaurant attached) is about ten minutes away from IAD. They've also got some affiliated bars inside the secure area of the airport, but at the brewery there's typically more than 30 different styles of beer, all made in the next room, on tap.

The Old Dominion Brewing Co. also gives free tours (with free beer) on weekends.

http://www.olddominion.com