Perhaps not quite so useful in the summer months, but what do you do when you're out in the cold of winter, or maybe late on a clear night, and you want to enjoy your music without the awkward and uncomfortable hat+earphones? make some muphones! or muffones.. or headmuffs.. its up to you :)
Since i made these i found out they have already been thoughtof :( as has the speaers-in-a-hat i also made a while back (though mine had an mp3 player builtin ;)) See: http://www.hearmuff.com/
This is my first instructable, and i'm making these for my girlfriends birthday.. go nerd presents!