I don’t generally use the internet for studying the Bible. I have lots of biblical commentaries, though (e.g. Ignatius Study Bible, Navarre, Catholic Commentary on Sacred Scripture, etc.).
For Catholic teachings, I always start with the Catechism. I would also seek out other Church documents on the matter (from Councils, Popes, and the Roman Curia).
I also have lots of Catholic books (both in print and digitally through Verbum) that I can search through depending on the topic.
If I’m looking for good articles that I can find quickly online and print off for someone, I would generally start here at Catholic Answers. I might also look at EWTN. The St. Paul Center is a good place to go for Bible study stuff. Even some of the Catholic news sites (like NCRegister) will have some good articles on Catholic teaching, too.
This works for me. I try to avoid unfamiliar sites from random people. At best, such places might point me to a primary source to go to instead.