I don't save or trade much any more. After more than 30 years in the same place, my garden is pretty full. And the fact that I've been wintersowing since 2006 contributes to the "my garden runneth over" thing.
Still, I do start a few things under lights every year and I still wintersow a few jugs every year, too.
Best bet for seed trades is the plant and seed trading forum. Lots of people do the piggy swap too, but I never have. Someone else will have to give you info on that.
Karen