Green Metropolis
Looking to sell books that are just acting as dust magnets. Well, there is always Amazon but if you want to do a little bit extra, have a look at Green Metropolis
You get a set rate of £3 per book, plus some postage costs if it's a larger or hardback book. They will also put 5p towards the Tree for All Campaign from the Woodland Trust
Okay, so 5 pence isn't a huge amount but it's still better than nothing and £3 is about what you'd get for a normal paperback on any auction site.