Price: $.40 (one stamp)
This is a little sketchy, but kind of funny nonetheless. When I was younger, I wrote a letter to 3M and told them I was doing a science experiment and wanted to know if they could send me different kinds of tape they had. They immediately sent me tons of different tape with an understanding that I would send them the science experiment after I used it. I think this would be a funny, although somewhat unethical, thing to do if you're bored. Yes, I am saying pose as a kindergartner. Hopefully you can come up with something better than 3M tape though.
Cheap and fun things to do around Minneapolis/St.Paul