I built a simulator to allow you to experience what it is like to type in Dvorak before committing to learn the layout. It assumes that you can touch-type in QWERTY. Enter some text into the first text box, and it gives you the equivalent keypresses to make [in QWERTY] that would output the same sentence in Dvorak.
https://github.com/osbert/dv-sim2
A former colleague of mine graciously contributed Colemak as an option as well.