I found this race today while looking for any Half-marathon between Jan and Mar 2010. Its a 3.5 hour drive from DC, with only a $20 registration fee. It also starts at noon, so you can drive out, not leaving until 7am, and get there in time without leaving super early. Its also the only one even remotely near DC during that time period. Half is on crushed limestone (not too crazy about that) but its held in a state park, and so I'm sure the scenery is nice.