Baltimore City has an abandoned motor vehicle auction every other Wednesday (I think) right off Pulaski Highway. Bikes are hard to come by at this particular auction. You could check auction notices in the paper - I believe they are listed in the classified section. Most of these are not insurance auctions, but stolen/abandoned vehicles that have never been reclaimed. They will have to be titled as salvage under MD law.
You can also check out www.ridesafely.com , they have a Philly and Morrisville location and have a constantly updated stock of cars and bikes. I bought my Duc from them and just purchased an M3, you have to be patient, but the deals are there.