Since you're in NJ, I guess I can help you without risking competition.
Local newspapers are good. I use auctionzip.com. I dunno if they service all zip codes, but they handle quite a few where I live. I search specifically for "lumber", and if the description includes the type (oak, cherry, etc) then I know it might be worth it. Otherwise, they probably just mean a pile of scrap 2X4's. Pictures are a big bonus on the website. And if the auction has a lot of woodworking equipment listed too, then it's a safer bet.