Check out this great ride locator:

Places to ride in the US

If I knew how to use a GPS, this would be a great resource:

GPS Adventure Rides

My personal favorite:

Tail of the Dragon-Dual Sport

I have now put about 6000 miles on my DR650, 25% on some great South Carolina dirt roads.  I would never have believed it but I already love this bike.  I put 23000 miles on my DR350 and 10000 miles on my DR250.  I no longer ride tight single track trails, so the heavier weight is not a big disadvantage.  I may change my mind after I drop the 650 in some of the famous SC mud.  I have never seen anything the consistency of this stuff.  Last fall I went through a long stretch of deep mud.  When I came to the end of the road, I stopped.  I could not get my boot off the footpeg.  I fell over almost like Arte Johnson on his tricycle on Laugh In.  I know I just dated myself, but that is the best description I can conjure up.