VirtualT is a high-fidelity emulator of the Model 100, 102, 200, NEC 8201a/8300, and the Olivetti M10.
It also emulates some hardware upgrades including Remem and Rampac.
VirtualT provides some debugging support, and facilties for easily transferring files to/from the guest operating system. Supported guest operating systems include Windows, OSX, Linux, and BSD.
The VirtualT project is hosted on Sourceforge, a popular web site which offers free hosting for free and open source projects.
All source code in the VirtualT project is kept in CVS. CVS allows complete tracking of all changes to the VirtualT source code. At any time, you can check out the "latest" code from CVS and build it on your computer. Instructions for downloading the source can be found in Building VirtualT on Ubuntu.
If you are building on Windows, you can start a Visual C++ Express Edition 2008 command prompt, and type
set FLTKDIR=c:\extsrc\fltk-1.1.7 msbuild
Note, you will need to change the path to FLTKDIR to whatever you use. This will build the entire project without having to fire up the GUI.
In addition to building from source, occasionally major releases of binary builds of the code are made. The download page for getting pre-built binaries is here.