ACTstudent.org
The makers of the ACT exam have come up with a few ways to prepare yourself for the exam without spending any cash at all. You can prepare with just a few practice questions for each test section, or pop over to their media area and download and print a pdf file of strategy, test tips and a complete free ACT practice test, including the ACT Writing prompt.
The Princeton Review
The Princeton Review, one of the most widely known test prep companies in the world, offers both in-person and online ACT practice tests for free! All you need to do is search for an available testing center near your zip code to take a test in person, or sign up for the online test. After the test, you'll receive a detailed performance report with personalized tips on how to improve your score. Awesome!
Peterson's
Peterson's, known for all sorts of educational publications like test prep, college preparation, college selection and more, offers a free ACT practice test, too. Here, you'll need to sign up for a StudentEdge account (which is free), and then register to take the online, timed test. After your test, your strengths and weaknesses will be assessed, and you'll be better able to develop strategies for the exam.
Number2.com
Number2.com, as in "Number 2 Pencil" has long been affiliated with free test prep. This company offers test prep – totally free – for the GRE, SAT along with the ACT. Here, although a practice test is not specified, you can go through an ACT tutorial with practice questions, get detailed, personalized progress reports, and even work with a coach or helper if you'd like.
Kaplan
This test prep company is the largest in the world, and with its propensity for offering worthwhile, free practice questions, tests, and even classes for those who can't or don't wish to pay, the sky's the limit for how large it can really become. With this Free ACT practice test, you'll get a meticulous score review, and even access to their ACT Classroom Anywhere prep course, which is top of the line.
McGraw-Hill's Practice Plus
You know what I like about McGraw-Hill's Practice Plus for the ACT? There's no sign-up or sign-in. You merely go to the website, select the practice test you'd like to take and start. That's it. Easy as can be. Here you'll find not one, but TWO online practice tests with explanations for every question. Bonus? Problem-solving videos and other ACT test prep materials like tips, strategies and how-to's. Love it!
This site!
Here on the Test Prep portion of About.com, there are some resources available to you, as well. Just like everything else on About.com, these ACT practice questions are completely free, too!