How can I find small, casual community events in a new city beyond listings?

[JustinFH]

I recently moved to a new city and I'm trying to get more involved in my local neighborhood, but I'm finding it hard to discover smaller, more casual community events beyond what's advertised on the main city website. I'm interested in things like park clean-ups, book clubs, or casual sports leagues where you can actually meet people. For long-time residents, what are the best local resources, social media groups, or community boards you use to find out about these smaller gatherings and volunteer opportunities that help you feel more connected?