You might find some interesting examples and pieces on IndieWeb wiki, particularly their Education page. I’d love to see Matt add his example(s) to that page for others’ future reference.
I did a short demonstration of what the current website-to-website space looks like at the recent OERxDomains21 Conference. You can find the short video here on my site.
If you go the older route one of the best planet-like sites I’ve seen was http://connectedcourses.net/, which if I recall correctly was built by Alan Levine. If you poke around a bit or ask @cogdog on Twitter, I think there are some details or a recipe somewhere of how he put it together.
Chances are reasonably good that people in the #DS106 or #DoOO space have some ideas as well.