TI Graphing Calculator Emulator
VTI is a virtual Texas Instrument graphing calculator emulator. It can emulate any model TI graphing calculator. Currently, it will only emulate the TI-89 graphing calculator. I will try to get it to emulate others as well.
This program apparently is written by a person named Rusty Wagner and I can not vouch for its accuracy. You should only use the ROM version if you own the graphing calculator.