The two best free practice platforms I've found:

1. Amphetype -- https://code.google.com/p/amphetype/
Amphetype is great for it's simplicity and flexibility.  My only thing is there aren't ready-made lessons using smaller words and single letters, which helps in the initial phases of learning (and relearning;-)).  Then I discovered this:

2. Typing practice -- http://gwydir.demon.co.uk/jo/typing/
Brilliant.  Simple, easy to access, turn it on and burn.  You can set it for single letters, two- or three- letter words.  You get positive reinforcement for small, bite-sized accomplishments on which you can build more sophisticated accomplishments.

Keep practicing!