In case anyone is not aware, Craigslist is an excellent resource for
finding mechanical musical instruments: http://www.craigslist.org/ 
However it's pretty much designed for "local" advertisements.  There is
another site  http://www.craiglook.com/  that uses RSS to aggregate the
listings on Craigslist so that they are searchable on a more national
level.  I've created a few URLs that may be helpful for people trying
to find free or cheap player pianos.

Click on this link to find all the player pianos listed as "free" on
Craigslist:  http://www.craiglook.com/all.html?q=free+player+piano 

Click on this link to find all the player pianos listed for sale _or_
free on Craigslist:  http://www.craiglook.com/all.html?q=player+piano 

This link will reveal pipe organs for sale:
http://www.craiglook.com/all.html?q=pipe+organ 

Now that you are aware of the site you can use it to search for
whatever mechanical music instrument type is of interest to you, e.g.,
music boxes, organ grinders -- you name it.

I have no affiliation with either Craigslist or Craiglook but I thought
this would be a great way to get buyers and sellers together to help
preserve these wonderful and deserving (of care) instruments.  I have
"restored" a few old players to working condition and then have given
them away to help encourage interest.  It's a great hobby and I plan to
continue to do so.

I've been reading all the articles and discussion about generating
interest in young people.  That can be accomplished with some ease.
If you want to generate interest in anything, the word "free" goes
a very long way.  You would be surprised at the interest you can
get when you advertise a player that is working.  The interest is
compounded greatly when the price is free and/or the advertisement
is well crafted in an interesting, amusing, and informative manner.

Happy hunting (for bargains),
Paul Meehan