Not sure about vintage appliances, but for quite allot of other things, the people to know are those involved in real estate/home construction/renovation. So many homes are being sold, especially by older folks cashing in on sky high housing prices these days. Many times people either leave stuff behind because they are moving to smaller digs and or new owners just rip out everything and chuck it to the curb. Cannot tell you how many fleaBay auctions I've seen with "found this in a house we just bought/are renovating/etc".
Scout around for homes for sale and if you really have nerve make an appointment to take a look. While you are "in" scope out appliances and ask if they are being sold with the house. You "may" be able to strike a deal to get the appliances. Make up some classy business cards for handing out to real estate/construction persons informing them what you are looking for. Don't appear over eagar or something someone considered "worthless trash" may all of sudden become worth $$$.
Just my two pence
Launderess