I just released Keyzen-Colemak, a typing trainer optimized for learning Colemak. This project is a fork of "keyzen," a free open source trainer designed for QWERTY.
Keyzen-Colemak is designed to emphasize characters vs. words, which makes it particularly valuable for programmers and brand new Colemak typists.
The trainer begins on the home row, and adds new characters automatically as you improve. (When you hear the "ding," you've leveled up!)
The character set is adjustable: clicking on the top bar allows you to select how many characters the trainer uses at any given time. When you make mistakes, the program starts to emphasize your problem characters, so you spend most of your time practicing the characters you miss most often.
I'm using this program to learn the layout as quickly as possible, and I'm finding it very useful. I hope you enjoy it!
