I recall a while back that they had a group buy of the Great Palace Vine pen kits and such ... that was hosted by one of the IAP suppliers!
http://www.penturners.org/forum/f218/great-palace-vine-preprod-now-134095/ It looks like it was hosted more through their own subforum rather than through the group buy subforum, but I think it was an excellent deal. It's too bad these pens were way out of my price range at the time! One of these days, I'm going to try out one of those "Trust Smitty" package deals, I hear those are awesome too!
There were also recent group buys (within the past year and a half I've been here) for: smocks, metric tap and die sets (2 start, 3 start), bog oak blanks, and the latest one that's currently going is one where someone's buying mass quantities of dowel hinge pins from china at huge discount to parcel out...
The participants of that last one (I'm one of them) are kinda already set, though someone may back out before he gets them in and asks for the payments.
You just need to keep an eye on the group buy subforum in order to get in on these deals!