I have a bag of books that's sitting in my room waiting for me to add to it, then I'll take them to the charity shop. Although by charity shop I mean one of the five in town. But I think some of them are a bit unlikely to sell in this town. And I know a lot of people keep talking about book swapping sites, so I thought I'd maybe investigate them since maybe it would lead to me buying fewer books.

So which ones do people use? Bearing in mind I have to be able to swap with people in Britain - I'm not planning on sending any overseas because that'll just be more expensive than buying them.