The ACT website: www.act.org
Good Sites for practice and study:
https://benchprep.com/act/games
https://www.learnerator.com/
http://www.freetestprep.com/index.php
http://www.studyguidezone.com/acttest.htm (prep for several different tests, including CLEP)
http://www.sparknotes.com/testprep/books/act/
http://www.varsitytutors.com/act-practice-tests - Has detailed scoring to help you find your strengths and weaknesses.
Geometry Review:
Khan Academy Video tutorials: https://www.khanacademy.org/math/geometry
Tutorials with quizzes at the end: http://www.math.com/homeworkhelp/Geometry.html