Steven Horowitz, who is the author of JetWit is working on getting a comprehensive list of JETs and drawing connections with sister cities. Here is an excerpt from the Jetwit page dedicated to this:
Welcome to the JET-Sister City List Project!
The Goal: To create a list of Japanese cities (and prefectures) where JETs lived that have a sister city relationship with another country.
How can you help? Email email@example.com with your name, prefecture, city/town and years on JET as well as any sister city relationships that your town had. If you already see your city listed, email your name anyway so we can include you as well.
The Result: JetWit will add to the below list as responses are received.
The Purpose: To lay some groundwork that may help Japanese cities/prefectures that hosted JETs increase their “return on investment” from their initial investment.
Here is the url for Steven’s Project: http://jetwit.com/wordpress/2010/10/30/jet-sister-city-list-project/
There is a link on there which takes you to a page showing all of the US-Japan sister city relationships so you can easily determine if you can be added to this list!