HAVE: 'Ice plant' and jade cuttings for native cacti
This is no big deal where I live (California), but I have access to about a half-dozen kinds of succulent ground-cover plants, mostly species that originate in South Africa or the Mediterranean. These include Carpobrotus, Aptenia, Mesembryanthemum, Senecio, and I think Lampranthus. Likewise with jade plants; there's one on every corner. These would all be good for potted plants in colder states, but they'd probably have to come indoors in winter. All easy to propagate by cuttings.
If you live in the U.S., I'd love to trade some of these for seeds, cuttings or whole cacti and succulents native to your state. (However, no prickly pear or cholla! I just don't have room for those thorny menaces!)
I'll consider swapping for other plants as well.