Becky, thanks for the tip about Bookmooch - it's much better than ReaditSwapit! I'm sending out my fifth book and have 2 on their way to me. :)
I've deleted almost all of my inventory from ReaditSwapIt, it was getting so frustrating - not a single swap worked out from a number of offers and requests.
You don't know a similar site for videos and DVDs, do you? I looked at TitleTrader (?) but they didn't seem to have anything I searched for, probably because if they did exist, they were in the US and wouldn't post to the UK.