Sites about Turing
1. http://www.turing.org.uk/
(If you hunt around, you can find a simulator on this site, but there
are more direct connections below.)
2. http://plato.stanford.edu/entries/turing-machine
You can find Turing Machine simulators on the following two sites:
3. http://www.ams.org/new-in-math/cover/turing.html
4. http://www.igs.net/~tril/tm/index.html