Two on-line Learning Styles Interactive Diagnostic Screening tools designed by Ross Cooper (LLU, South Bank University). They do not rely purely on reading skills and are best explained by reading parts of the handbook (see note below).
Version one focuses on learning styles (visual holistic, visual sequential, verbal holistic or verbal sequential), version two also includes dyslexia screening.
Editor's note (Sept 2018)
Now hosted by Outsider Software. The handbook is here. Explore the new site carefully to find the screening tools (some links are dead). One interactive screener starts here, I haven't found the second screener .