Like the title says 5 things you think can help generate trade between towns.

1)Carts
2)regional resources
3)unique (few per town) and useful recipes, 3 missions that give unique recipes witch can be crafted once, missions can be repeatable one every week or so but require rare resources (maybe not easy).
4)Dezgard's barter village that accepts one type or currency for cosmetic changes to armor and weapons and maybe simple recipes like baskets
5)paved road tiles that require stone=15% speed Bricks=20%

fire away