I've found two very interesting 'book recycling/auction/swapping' - type websites, which are both based in the UK.
The first is a place where people can simply swap books with each other, without any charge for listing books, and no cost other than postage (which each person pays for their own book, as it's sent out).
People just build up a list (however humble or meagre, to begin with) and can then approach anybody with a nice lookign book in their list, and ask whether they might like one of your own books in exchange.
You might get turned down a few times, but I've swapped out quite a few books in my time.
And most of mine weren't even all that good, the ones I put up there.
It's a good community, and the range of books available is really good.
(1) Read it Swap it -
http://www.readitswapit.co.uk/TheLibrary.aspxThe second place, I've just found.
It's an auction/recycling website, in the style of Amazon.
About halfway towards being ReaditSwapit, this is a similar place.
The main difference is that it uses a system of charging for books, whereby people pay £3.75 to buy every book which is listed on the website, and people are paid £3 of that money for every book which they sell there.
5p of the money from each sale is donated to the Woodland Trust, which is nice as well, and I think that overall it seems a bit more secure. I think the whole system is really nice, and it seems well-run etc.
I've just recently found this website, so I've yet to sign up any books with them.
But, it'll be good to try it and see how I get on.
(2) Green Metropolis -
http://www.greenmetropolis.com/ ~ yay !