My goal with this thread is to gather simulations that are HP-like. So here is the collection, with my own HP-Likeness indication. Software authors take note: HP-Likeness is important!
1. HP-12C simulator
http://www.kktechnologies.com/kk-12c.html
Very faithful HP-12C simulation, including programming. Very clever and functional solution for simulating the voyager keyboard on the palm screen.
HP-likeness: 8 out of 10
2. HP-41CX emulator
http://www.berndabel.de/products/coconut/index.html
Very faithful HP-41CX emulation (uses HP-41CX ROM) - much better on color.
HP-likeness: 9 out of 10.
3. HP-41CV emulator with roms
http://www.palmgear.com/software/showsoftware.cfm?sid=34175820020914001146&prodID=40123
Not as faithful as coconut, but the author is working on it. Very interesting ROM modules management.
HP-Likeness: 7 out of 10
4. Scientific Programmable, no specific model, but a true RPN
http://www.creativecreek.com/mathupro.html
Does not emulate a real HP model, but creates a surprising level of likeness. Very interesting functionalities.
HP-Likeness: 8 out of 10.
5. HP-16C simulation
http://www.palmgear.com/software/showsoftware.cfm?sid=34175820&prodID=40784
Complete (as far as I know) functional simulation of 16c, but a keyboard like KK-12C would improve HP-likeness very much.
HP-Likeness: 7 out of 10.
6. Other RPN calcs
There are at least 6 other RPN, with very good functionality as a RPN calc for palm. As HP-likeness is below 5, I donĀ“t list them here.