IUC in Yokohama is a short 10 week intensive program. It's -very- intense though and only for intermediate to advanced learners.
It is expensive, but if you get accepted to the school you will probably receive a scholarship that covers most all of the tuition.
I wrote about it here, check it out.
www.japannewbie.com/2007/10/14/iuc-in-yo...an-advanced-student/