Actually you should spend 1/2 your time in Silicon
Valley
(see:
http://www.kce.com/junk.htm ). After that all else
pales.
I wish it were still true, but eBay has infected almost every place on your
list. They may not know what you have, what it does, or if it works, but
they sure know what one sold for on eBay once. My guess is that some good
sources do still exist, but nobody wants to risk someone infecting them. ;)
Places I like to find are the scrappers, places where people bring loads of
circuit boards etc. School surplus sales, where all the local auction
listings get published, thats the hard to find, but worth it information.