Maryland Park Service Passport

[7rider]

I have the same view and concern.
I checked out DNR's website. They have lists of regional areas, by activity. Here is the link for areas with trails open for biking: http://dnr.maryland.gov/outdoors/biking.html
In Western MD: Gambrill is very popular, but very technical (I've heard -- rocky and hilly).
In Central MD: Seneca Creek, Patapsco, and Gunpowder are popular areas.
In Southern MD: Rosaryville is a favorite for some of us TE'ers. Merkle was muddy but pretty the one time I went there. Great kayaking, tho'!
Can't speak for Eastern MD. I imagine there isn't much singletrack aout there, but rather, fire roads and paved and perhaps gravel roads. I've been out to Jane's Island (which also has kayak trails) for some fishing. There's a campground there that looked nice, if you're into that!
The MORE site also has a link in their forum "Where to Ride" that id's some places.

Several TE'ers are also kayakers.
Here's the link to kayak and canoe trails with the State Park system: http://dnr.maryland.gov/outdoors/boating.html

And, of course, hiking: http://dnr.maryland.gov/outdoors/hiking.html