Here in Wisconsin we have "COWs" (http://www.couplesonwheels.com/) from the Wisconsin Tandem Club. Their rides always seem to gather a decent number of participants.
I have a tandem, bought new a week after my wife and I were married, but due to hip trouble she has been unable to ride it for many years now. My daughter and I take it out a few times a year to shake the cobwebs off.
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-John Thompson (john@os2.dhs.org)
Appleton WI USA