For those of you who like directly read the original scientific literature on ADHD, autism, dyslexia, or learning in general, here is a nice site which keeps track of journals with free text. Because the NIH only asked (i.e. not forced) medical publishers to post their articles by NIH-funded authors on the web, many journals have decided to share them only after 6 months to 2 years. Still, that's better than it was before.
The Free Medical Journals Site