The following are more advanced sites:

Ravi Zacharius International Ministries

Christian Research Institute- is an apologetics ministry responding to cults, world religions, attacks on biblical reliability, etc with an archive of free articles. www.equip.org

Spiritual Counterfeits Project- offers Christian responses to Eastern religious movements, cults, self-help and New Age thinking. www.scp-inc.org

Stand to Reason- is a ministry that offers a number of useful resources on a range of topics including apologetics, bio-ethics, philosophy, science and theology.www.str.org

Reasons to believe - integrating science and faith http://www.reasons.org/learning 

CS Lewis Institute http://www.cslewisinstitute.org/