RPN

Eric Smith's HP Calculator Info
Technically page about older HP calculators with simulators for HP-41 and 45 calculators. With links to other calculator-related pages, journal articles, and US patents.
http://www.brouhaha.com/~eric/hpcalc/

User Friendly the Comic Strip
about RPN. A good way of explaining RPN with three picture frames. (Note: Erwin is an AI entity that frequently has been moved to different computers and his previous home was a Sun Workstation.)
http://www.userfriendly.org/cartoons/archives/99aug/19990826.html