I second the MacArthur loop. there's a group ride going on a regular basis if you're interested. check www.dcvelo.com. Make sure you go up the hill at Old Anglers' Inn, go down to Great Falls (MD side), back up, back DOWN to OAI, backtrack about a mile, and then take a left onto Brickyard Rd. There's a great hill workout to be had there.
have you every been out to Sugarloaf? Get yourself a DC cycling map, and you should be good to go. They have them at most bikestores. WABA (wash aread bicyclists' assoc'n) also has a '50 rides in and around Washington' that can be helpful. Potomac Pedalers are also a wealth of information - I know folks who ride w/ them and love it.
Weekends, I like to go out Beach Dr. (mostly closed for cars, cross the East West Hwy, then go up the Mormon Temple Hill, and continue out until the end of Beach Dr. Classic DC ride also.
At the right time (weekdays, mostly, weekends before 10) going up the Capital Crescent trail is a good time.
Josef
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