The website I've used the most is, but mostly just because it assembles many features into one place, including creating an account and tracking progress, as well as a lot of variety in practice/testing.
I relatively recently took on the monumental challange of throwing Qwerty out of the window, I rearranged my keyboard keycaps to Dvorak, so I've been doing a lot of practice and tests.
So many terrible typing speed test/practice websites.
