TI-99 4A

MacV9T9
A TI99 Emulator for the Macintosh, by Raphaël Nabet.
http://pytheas.club.fr/english/TI99.html

PC99 Menu
Shareware front end for PC99. Allows you to easily change modules and disks.
http://www.btinternet.com/~shawweb/stephen/TI.htm

TI-99/SIM
An open source emulator for Linux/Unix and Windows.
http://www.mrousseau.org/programs/ti99sim/

Ti99/4W
Freeware emulator for Windows.
http://home.wanadoo.nl/fgkaal/software.html#ti994w

The Tutti Emulator
TUTor Tiny Implementation - an emulator of Tomy Tutor for Commodore 64 and disk drive.
http://www.floodgap.com/retrobits/tomy/emu.html