I'm curious to hear other's thoughts on they think would be useful.
Please don't hold back ideas! There's very little harm positing silly or unlikely ideas, but there is some potential value (perhaps more than you realize).
Inspired in part by calebo's comment here
I know there was one Discord group for rationalists learning math that seemed pretty useful.
Separately, there's been a decent amount of work on AI specifically. I was personally matched with a few other people near me to learn about ML, and we did have several sessions, which was pretty nice.
I'd encourage more experiments here. One common thread (you'll likely see in several responses) is that I'd encourage you to think small at first, as in an MVP. Maybe some early versions would look like Slack/Discord groups for one specific niche.
If you (anyone reading this) are interested, I recommend applying to the EA Funds or similar. I imagine some interventions here may be quite cheap, but useful. I'd be happy to review your application or discuss if you do.