Authors of PC99, a TI-99/4A emulator for the PC. Description as well as program, manulal and command module order information,

A TI99 Emulator for the Macintosh, by Raphaël Nabet.

Shareware front end for PC99. Allows you to easily change modules and disks.

TUTor Tiny Implementation - an emulator of Tomy Tutor for Commodore 64 and disk drive.

An open source emulator for Linux/Unix and Windows.