I'm not sure what the condition of the trail is like these days, but Fountainhead is a short drive (depending on where you are in Alexandria).
Shaffer Farms is fun, Gambril is good both in MD
If you don't mind a bit of a drive, Elizabeths Furnace is nice & technical long climbs fast downhills. If you leave early in the morning, you can ride a good 4 hours out there, and still make it back for a night ride (if you have legs left). Check the MORE board for any rides that may be going on www.more-mtb.org
Shaffer Farms is fun, Gambril is good both in MD
If you don't mind a bit of a drive, Elizabeths Furnace is nice & technical long climbs fast downhills. If you leave early in the morning, you can ride a good 4 hours out there, and still make it back for a night ride (if you have legs left). Check the MORE board for any rides that may be going on www.more-mtb.org