A rich example of how badge learning can be implemented to support authentic, project-based, student-interest driven learning. This is a program at UC Davis. What pieces of their program could be applicable to a grades 6-12 setting, where badges offer feedback, learning milestones, and open up spaces of possibilities for learning?
I am a big fan of WebQuests because they can be individual, pairs, or group and they're student driven which allows the teacher to be there for support when needed.
This site has a lot of good information and is just right for Middle School students. Grade 5 students can also use it but would need a little more guidance.