We have been doing a lot of unit studies...not really for any specific class but they are more for my oldest to "get in" the electives that he is interested in...
Right now we are doing game development, caring for goats and guineas (two animals we have on the farm right now, and survival skills.
I will probably make more of these into a credit depending on the level of research and work he does on them..more of hobbies for him.
What are you doing for extra credit/unit studies/etc. for your kiddos?