Here's a nice app from our friends at RTS that helps you memorize the Westminster Shorter Catechism--one of the most outstanding summaries of Bible doctrine ever written--in 90 days.
(For those unfamiliar with Presbyterian catechesis, the 'Westminster Standards' are three inter-related documents that came out of the British ecclesial meetings of the 1640s at Westminster Abbey in London--as opposed to the Dutch Reformed confessions such as the Heidelberg Catechism or the Belgic Confession, which were formulated on the continent, and which are equally magnificent. The Westminster Standards were later adopted by the churches of Scotland. The three documents are:
1. The Westminster Confession of Faith - a topically arranged statement of Reformed doctrine in 33 chapters, with 5 or 6 explanatory paragraphs in each chapter, accompanied by meticulous Scripture proofs.
2. The Westminster Larger Catechism - the doctrine of the Confession of Faith put in question and answer form for the purpose of catechesis. This is the document that famously begins 'What is the chief end of man? Man's chief end is to glorify God and enjoy him forever.' And so on.
3. The Westminster Shorter Catechism - a condensation of #2, the Shorter Catechism serves the purpose of  enabling children to learn the doctrine of the Standards and  enabling 21st-century PCA ordinands to avoid memorizing the Larger Catechism in being examined for licensure and ordination.)