This link will work on reading comprehension. It is a test with answer explanations!
This link will help you specifically with reading comprehension skills for the ACT.
This link is great for help with inferencing questions on the ACT.
This link that will help with the comparative skills needed to master the more difficult questions on the ACT.
This link will help you with the conflicting viewpoint passage on the ACT. Remember they rotate where it is so you need a technique for whatever passage it is in.
This link is a great read from Method Test Prep on how not to get beaten on tricking reading questions.