Homestay in Japan. Here's a link to the program I went on.
http://www.centerforstudyabroad.com/japanese-language-institute/
Extremely good experience. I'd do it again in an instant (in fact, I'm prob gonna do it again this summer). There are two classes, one for speaking (grammar, vocab, etc.) and one for writing (you will learn both phonetic alphabets). There's 6 different levels, and they test you at the beginning to place you. You also get field trips to some cool places... including Kyoto and Himeji.
It's amazing what you can learn in one month when you're actually there experiencing it. It would take 5 years at least to learn what I learned in a classroom here.