Does anyone else find it deliciously ironic that, in such a pro-Unix article, Miguel recommends Mavis Beacon? According to Amazon, it's available only for Windows and OSX :p
Then I picked up computers as a hobby. With all the random typing I did as part of the hobby I quickly found myself in the 70-100 WPM range.
You don't really need a typing tutor program with its learning modules and fluff. You just need to spend time typing. I recommend printing out a color-coded image[1] of a keyboard that shows which fingers to use for which keys and just spending a little time on http://typeracer.com every day trying to stay on home row and follow the color guide.