If you haven't seen it already, you should check out this week's NYTimes.com Numberplay blog by Gary Antonick, which features a discussion on a Mad Veterinarian puzzle led by Joshua Zucker:
http://wordplay.blogs.nytimes.com/2011/06/27/numberplay-the-mad-vet/#more-66893
Note 3 mentions MTCs and links to the MTC Network website.
Best,
Brianna Donaldson