We had an exchange student from Germany live with us for a semester last year (attending the local high school), and we enjoyed it very much. I thought I’d plug the program we used, the Academic Year in America program from the AIFS Foundation. (Apparently they like to do full academic years, but one can also find students who only want to spend a semester.) Students in this program can come from any of about forty countries in Europe, Asia, Africa, or Latin America; there are probably other organizations out there that handle different countries. If you’re interested in this sort of thing, let me know.