Framasoft has released Mobilizon, which is a self-hostable, federated webapp for event management.
I believe it’s a great step towards making emigration from Facebook practical. Event planning, organization, membership, and discussion is a powerful feature that keeps many of my friends in Facebook, so if I can get a convenient replacement for that service, I may be able to wean them away.
It’s a bit unintuitive in terms of steps needed to create an event and share it with people. It took a good 10 - 15 minutes of playing around in the interface to figure out how to create a group, and to create an event and share it with the group; which is actually a lot of friction if you’re trying to convince people en masse to use the service. There’s also minimal customization to the aesthetics/visuals of the site (for now) - It is open source so customizable, of course, but convenience for the end-user would be a big win.
Despite its flaws, it’s very useable and seems very useful. We’ll see what issues I come across when I get a chance to really use it for organizing an event.