Casio CFX 9800G Emulator
You can run the emulator here.

At school, I had a Casio CFX 9800G colour graphing calculator. It had a simple programming language and I used to while away some more boring lessons by writing games and drawing pictures. This was back in around 1998.
I kept the calculator. From time to time, I would find it in a drawer and look over my old programs. The battery-backed memory had lasted more than ten years on standby, but I realised that it wouldn't last forever, and that made me sad. In a fit of nostalgia, I resolved to copy the programs onto a PC, where they could live forever.
Now I just needed a way to run them. Casio have released an official emulator for the "fx-9800G USB" (you can download it here), but that's a slightly different machine. Although it's a more advanced model, with a slightly better programming language and more functions, it's only black and white; the screen is also slightly larger. So none of my old programs ran correctly on the emulator.
I searched for quite a while for an emulator for the colour calculator, but in the end I gave up and wrote my own. Here it is.
If you want to read the source code, or read more of the technical details, then visit the GitHub repos for this project.
(I also patched the old programs so that they run OK on the black-and-white emulator, corrected for the different screen width. The details are on GitHub, if you're interested.)
The Programs
The programs I still had stored on the calculator are:
p0-poisson.txt
Calculates probabilities in the Poisson distribution, and keeps a running total. An uncharacteristically legitimate mathematical program.
p1-powerseqs.txt
Solves for the coefficients of cubic or quadratic sequences, given the first few terms.
p6-mandl2.txt
A rendering of the Mandlebrot set
p7-bse.txt
This is a (somewhat dark) simulator where you play a cow culling business during the BSE cull days.
p8-master.txt
This is my re-imagining of a game I used to play on the BBC Micro. (It's much worse than the original!) You are in charge of a village and have to decide how much rice to plant v.s. eat each year.
p9-casino.txt
A slot machine simulator. The payouts are fairly generous, so it's easy to become a millionaire (with patience).
pC-dice.txt
This is an implementation of a dice betting game I saw in a computer game on the Acorn. It was a medieval themed game; I don't know if this is a traditional dice game, or was made up for that computer game.
pD-mastermind.txt
This is an implementation of the Mastermind guessing game. The computer will think of 4 numbers 0-9, and you have to guess by entering a four digit number. The computer will answer with the number of "hits" (exact matches by digit) and "halves" (the right digit in the wrong column).
pE-cccp.txt
A rendering of the USSR flag.
pF-fibbonachi.txt
Generates the fibbonachi sequence.
pK-island.txt
A pretty picture.
pM-banner.txt
The Nazi flag.
pN-union-jack.txt
The UK flag.
pO-tricolore.txt
The French flag.
pP-swiss.txt
The Swiss flag.
pQ-poly-area.txt
Computes the area of a regular polygon.
pRho-star.txt
Draws a star.
pR-palm.txt
A pretty picture.
pV-fireworks.txt
An animation of fireworks.