By far the most challenging for those who do not believe in God is a notion of design in nature. Many scientists would deny and discredit the design for a simple reason, that they would have to answer for their unbelieve to the designer. For "where there is a design there must be a designer or creator" in the same way as "where there is a watch there must be a watchmaker". The simplest design like a "bird feeding house" in the middle of the forest will sugest that there is/was someone here who made id, and yet so many people looking at the DNA helix, complexity of which we don't even begin to understand, say it happen by accident, chance, evolution. This is a perfect example of denial and defience. Many times people will say that Christianity is made up of the people who have been brain washed to belive inspite of evidence, but the eveidence "have been clearly seen, being understood from what has been made, so that man are without excuse" Rom 1.20.
Creation Ministries International (http://creation.com) is at the fore-front of this information battle. So, if you just want to be well informed or you need more courage to talk with your friends and relatives this is the place to visit. CMI website is updated daily, with responses being posted to the latest evolutionary claims and findings, plus thousands of articles from the past years makes that site "a must to visit".

For a reformed christian the apologetics page at reformed.org/apologetics/ is a Treasure Island among the sea of unbelief.

The 'Subordinate Standard' of the PCV and most other Presbyterian or Reformed churches around the world is the Westminster Confession of Faith, which can be found together with a range of other important documents at reformed.org.