The following webpages/websites present a relatively nuanced interpretation of the doctrine that there is no salvation outside the Church (Extra Ecclesiam Nulla Salus), seeking to take into account all of the theology sources and points of references, from the Scriptures to the present-day Magisterium.
Overview of various Church Fathers, Doctors, and Magisterial Texts (on this site)
These webpages/websites present a more one-sided and rigid interpretation of the doctrine, relying upon certain older formulations, and either rejecting the recent teaching of the Church, or insisting that the recent teaching must absolutely be backwards interpreted to fit the earlier teaching as they interpret it.
Brochure on Extra Ecclesiam Nulla Salus (No Salvation Outside the Church)
Articles and blogposts on "Outside the Church there is no salvation" at Catholicism.org
www.pathsoflove.com