ACT Prep Apps
http://testprep.about.com/od/ACT_Prep/tp/Top_5_ACT_Apps.htm
ACTStudent
Maker: ACT, Inc.
User Ranking: 4/5 stars
Price: Free!
AllenACT
Maker: Allen Resources, Inc.
User Ranking: 3/5 stars
Price: The original download is free, but that only comes with a handful of questions. To get the real prep, you'll need to do some in-app purchasing. The full version of their ACT test bank, with over 1000 questions, is $4.99.
ACT McGraw Hill
Maker: BenchPrep
User Ranking: 4/5 stars
Price: $19.99 with optional in-app purchases of $1.99 for additional practice tests
ACT for Dummies
Maker: gWhiz, LLC.
User Ranking: 3.5/5 stars
Price: $9.99
Shmoop ACT Test Prep
Maker: Shmoop University, Inc.
User Ranking: Not yet rated
Price: $4.99