The following is a list of different sites I recommend. All are intellectually stimulating and will challenge even the toughest critics of the Faith.
mark mallet

I have followed this gentleman for over 12 years. He has lengthy posts, but all of them are relevant to our times. An award winning journalist, he has been led to create a site filled with insightful commentary and encouraging writings from a Catholic perspective. He is a singer/song writer as well, offering beautiful compositions for those who enjoy good music.
the catholic gentleman
One of my favorites, for his intellectual curiosity.

word on fire
Bishop Barron is a highly intellectual man. His deep insight into the human condition and the Catholic Faith appeals to all from different walks of life.
dr. scott hahn
A former Protestant pastor, now Catholic apologist. One of several who tried to prove the Church wrong through both Bible and historical documents…failing miserably in his attempt. he not only converted, but converted his family and friends along the way as well.
jeff cavins
An American Biblical scholar and apologist. He is one of the most humble men I have ever met. And his deep insight into the Catholic and Jewish teachings makes the entire experience of reading the Bible through the correct lens an unforgettable experience.
ewtn
This is the most comprehensive site and media outlet available worldwide. The brainchild of Mother Angelica, the resources are all freely available for the curious and those who are seeking the Truth. Even those who wish to challenge the teachings of the Church can find information and people who can answer even the toughest questions.
catholic business journal
A great resource for up to date Catholic insights and current events worldwide. A business news site, this is linked to a radio show called, The Mentors Radio, for business owners and want-to-be business owners. Excellent information here.