This is my implementation of Langton's Ant (a popular turingmachine, see http://en.wikipedia.org/wiki/Langton%27s_ant for more information) using C#. Supports multiple ants and threading. Video: http://www.youtube.com/watch?v=Vu9C_1DH31k
Tuatara TuringMachine Simulator is a graphical tool for designing and executing Turing Machines. Designed primarily for teaching purposes, it features a simple point-and-click interface.
Visual TuringMachine is a tool for visually designing Turing machines. This means no coding in abstract scripting languages, but simple point&click design. It uses the a..z symbol set, plus the "empty" # symbol, and also simulates an infinite tape.