People are regularly doing Simultaneous Multilateral Barter
at the
boardgamegeek.com website. It would be great to
extend their experience and methodology to more general
bartering. Also, they use various algorithms, so they might be
willing to participate in experiments of various system designs.
They call them "math trades".
Guide to math trades:
http://boardgamegeek.com/thread/93555/math-trade-guide
For examples, go to "geeklists" on that website and search
for "math trade".