Every year one of the more affluent suburbs near D.C. has a "spring cleaning" bulk pickup where residents clean out their garage and put things out on the curb for the city to pick up. It's a well-known thing, and we drive around in our minivan with all the other "pickers" looking for valuables. I have to say, it's the best place I've ever found to look for bikes. I usually end up donating them. This year I picked up an '88 Haro Sport freestyle bmx (traded straight across for the Alpine with full campy NR), a Specialized hybrid, and a GT hybrid. The specialized brought $70 untouched, and the GT was donated. I usually come back with at least an old Trek mtb or two. Two years ago I brought home the '85 Peugeot PGN-10, plus a couple of donate bikes. Eight years ago I brought home the '81 Soma Competition (now sold).

So, be inventive when you're looking, be persistent, and post pictures when you do get it!