ACK! How do you accidentaly sell borrowed books? Sorry, that doesn’t help. But it does remind me that I need to make a list of which of my friends have borrowed which materials – if for nothing else than I can periodically ask them how they are enjoying using MY “suchandsuch” a book. 
There is a Yahoo group for used math u see curriculum to be sold – just go to Yahoo groups and join the MUS Swap group. I’ve bought blocks from there as well as several years worth of used curriculum – even getting UNUSED student texts! It’s the best! Hope that’s helpful!
Rebekah