I'm thinking of something about Planetary and PlanetMath, based on the idea of organising a course "around something I plan to be doing anyway".

I'm particularly interested in peer learning for mathematics, and have for some years felt that mathematics should work "more like free software". There are a whole range of possible outcomes associated with that, but over the next 1.75 years the main topic of concern for me is building a peer-supported problem solving workshop for university-level mathematics. The desired outcome is that this continuous online workshop will be more effective for many mathematics learners than the traditional lecture/textbook/homework formula. That's not a lot of time, so many constraints are imposed, including on how I engage with broader efforts like the one we're discussing now. That said, I think a lot can be learned from the mathematics case, at least for related technical and scientific fields, and likely for any "knowledge-intensive" setting -- and viceversa, I think that there are some broad themes that need to be understood really well for any given special case (like math) to work.

If you're interested in joining in, hopefully we can work together to make the discussion mutually interesting ;)