If there was no money, we would all use Hive instead of course ;)
something that everyone can carry around and use to barter with...
Time, skills, and knowledge.
You grow vegetables. I come by and want a bowl of tomato soup. Maybe I trade an hour of weeding for my food, help chop the ingredients for the next batch of soup, give you my knowledge about what to plant between the tomatos to repel pests, tell you a recipe for onion leaf pesto, or spend some time drilling your kids in multiplication and teaching them how to play backgammon. There are probably hundreds of things I could do for that bowl of soup, that you don't want to do yourself, or don't have the time or skills for! I could help spell check your next Hive post, mend your rabbit cage, sort your library alphabetically by author and title (for more food and maybe somewhere to sleep, depending on how many books you have) or take your dog for a walk...