São Paulo, Brazil
I'm going to visit Boston during one month (November-2014) to study english and I'd like to visit the MIT campuses or Harvard campuses to do some workshop or one day class about anything to grow my knowledgments, experience and practice my english, some one know something about?
Look up the website edX (http://www.edx.org) and peruse through a list of courses that might pique your interest or help you practice English at your own pace/liking. Good luck
Unfortunately, neither school offers one-day workshops or classes open to the general public. The Harvard Extension School offers classes to the public but the timing does not work for what you want.