Last year, my in laws had an overabundance of fresh peaches, and my friends on their farm had a bunch of meat birds, so they traded a couple boxes of peaches for a few processed chickens for the freezer. Worked out pretty well... but the hard thing is finding two people who both have an abundance of something that the other person wants, at the same time. Which is why money was invented, of course. But then there's that pesky thing you mentioned without mentioning.
A regional bartering meetup kinda thing would be cool. For free stuff, I often watch Freecycle near my area (but all the best stuff is usually over the mountain 40 minutes away, and only worth it for large, expensive items). The most common "trade" that happens around me, however, is just sharing extra, as Riona mentioned.
My husband helped some friends of ours out with their excavator, helping to fix it. They gave us some honey. But it wasn't exactly at the same time, and nobody talked about payment or demanded an exchange of some kind.
People bring extra veggies to church in season when a surplus comes pouring out of their garden. Once a month the men get together early on a Saturday to discuss a book and then go to someone's house and help them out with what needs done. (Felling trees, splitting wood for a widow, putting a new roof on somebody's house, mulching.) When a couple has a new baby, there's a queue for making them dinner for a few weeks--and you'd better jump on the list fast, otherwise there will be no more spots.
I was talking to the lady who takes care of the plants around the church about gardens and flowerbeds, and she said that she's having to downsize her gardens and flowerbeds as she gets older, and could come by sometime with some plants if I wanted them and help me put them in. And I was talking to an older man about his apricot, which flowers too early and loses buds to frost, and he offered me plants as well. Another woman has an elderberry bush and offered me a cutting. At the moment, I don't have much to offer in return, but they're willing to give generously, and I'm very thankful for that. Hopefully I'll be able to bless them as well in the future, or to serve in some other way, but it's not a transactional relationship. No one's keeping count. We're all trying to give when we can.
I guess what I'm trying to get at is that, when you have a built-in community already like that, often the most wonderful things happen just from talking to people and from freely giving. These people have known me for over a decade, some of them since I was born (!), so that helps.
But... some people don't have a community like that at the ready. A sort of organized bartering/exchange system would be wonderful there. I'm imagining something like Freecycle, but for bartering...
My husband's bad experience with bartering came when he built something for a friend and was offered a motorcycle in exchange. The motorcycle wasn't what he expected--it needed a lot more work than advertised, and my husband felt a bit cheated, as the work he had offered was of much greater value. It's that difficult thing where working for friends and family can drive a wedge between people. For bartering there would need to be clear expectations up front. And perhaps not bartering with friends and family. I prefer freely giving and receiving with no accounting, anyway...
My good experience with bartering was when I traded help processing some meat ducks for a five gallon bucket of earthworms (and some cash). I had already been helping with chicken processing, and when asked to help with ducks, I proposed the earthworm trade. It was clear up front, and honestly I was prepared to be happy with whatever I received. I wasn't even expecting to be paid, too, so that was just a bonus.
My mother, a teacher, barters her help weeding and working at our friend's farm (same friend with the chickens) for part of a CSA share each week during the summer. She loves it. But again, we know these people from church, so that's where the connection started.