Back in February, I wrote about Scott Flansburg, who performs as the human calculator. This, in fact, is one of the entries that inspired the creation of this video section.
Probably the best introduction to his feats, if you're not familiar with him, is his appearance on the Oprah Winfrey show. From there, you can check out other videos, as well.
I bet you never expected to see Alice Cooper (Dial-up or Broadband) on Grey Matters, did you?
Update (10/31/06): Over on Google Video, I've found some more footage of Scott Flansburg.