Rob Cockerham of the wonderful Cockeyed.com has done many goofy experiments over the years, chronicling his exploits on his site.
But I recently became fascinated with one he did back in 2004. For the month of February, he ate in for every single meal (not necessarily at his home, but food he prepared himself). For the month of March, he ate out for every single meal (except for one mistake when he had a bowl of cereal at a friend's without thinking about it).
In true Cockeyed.com form, he detailed everything...how much it cost, how long it took, etc., and presented the results at the end of the months. No surprise, it was much more expensive to eat out, but he had a lot more fun doing that, he says.
And don't miss Rob's Halloween costume this year -- he was a box of See's candy! I think he was robbed in the costume contest, personally. You can also look at his incredible costumes from years past.