I know that the Type Flash game was intended to help children learn to type, but I've found that it is also very effective for learning to type on a chorded keyboard! Chorded keyboard? That's a one-handed keyboard, like the Infogrip BAT Keyboard that I'm trying to learn, which has only six or seven keys that are pressed in combinations -- chorded -- to simulate a full-sized 101-key keyboard. This is primarily for people who have limited capabilities, I only have one hand, but others may have visual or other impairments. And others' WORK may require typing with only one hand while the other hand manipulates a trackpad or trackball or mouse or even a touch screen. There have been a number of innovative chorded keyboarding devices through the years aimed at both those user groups.
Type Flash is the best app I've found to assist me learning chorded typing, and I've tried many. It may be just an illusion, but it seems as though Type Flash finds words that contain the letters that the user has just missed, which reinforces the learning!
This is a very easy program to use, with a very nice interface. It would be nice if, while the user is still typing slow enough to allow it, each letter press was announced with a recorded voice -- that would be useful to many learners, not only those with visual problems.
I really like Type Flash, it's a fun game. I recommend it!