flohmarkt is a self-hostable web application that can be used to show small ads that registered users may publish. These small ads are not limited to live on only the one server they were created at. Instead they can be shared among other flohmarkt servers as well as many other servers that are part of the fediverse (e.g mastodon-servers).

Really cute idea (like the old LJ sales journals/comms) and could be great for super-local communities.