Someone's put together a little CGI script that lets you figure out how much money you could have if you didn't go to, say, Starbucks and buy a coffee there, but instead got a coffee machine and made your own (or used an office coffeemaker).
http://www.hughchou.org/calc/coffee.cgi
(Seen at Andrew Tobias's blog)
http://www.hughchou.org/calc/coffee.cgi
(Seen at Andrew Tobias's blog)