A basic telnet application for Windows originally released at http://zetacentauri.com and downloaded more than 60,000 times before being open sourced.
A prebuilt installer is available in the installer directory here:
https://github.com/Xangis/ZetaTelnet/blob/master/Installer/ZetaTelnet3.01Setup.exe
This application was written using C# .NET 2.0 and should run on any system that supports .NET 2.0. A project is included for Visual Studio 11. It doesn't have any complicated dependencies, so you can create a project for an earlier version simply by including the source files.
This program has only very basic telnet support and doesn't support secure sockets (SSH) or any terminal protocols such as VT100 or VT52. I'd be happy to accept any pull requests if you'd like to add them.
Installer scripts for InnoSetup and NSIS are included in the installer directory, but you'll probably have to modify the paths in order for them to work because they assume things about development environment that is specific to me.