College Board has an app that allows you to take a practice test and practice one question a day!
ACT has ACT Academy where you can take practice tests and quizes you as well!
Some students use private tutors to prepare for the SAT or ACT. There are many available and the cost varies. Some organizations charge on a sliding scale (depending on your income), some give out scholarships and others are an investment. Most meet once (or twice) a week and are offered in a group setting. Come see me if you are interested.