Great idea! I was aware that cat litter is good for absorbing moisture in caravans, MHs etc, but putting it in an old sock, rather than in tubs with holes in the top, is a much better idea. Might have to give it a go ... I'll just have to nick some of hubby's socks when he's not looking!
I think there's going to be loads of people trying this idea, socks will be going missing all over the place.
What about an old draught excluder cut, emptied. re-filled with cat litter and then seen back up?