Maciej Wyrodek gives a great overview of the Agile Testing Quadrants model and shows how to apply it in different scenarios.
This is a great explanation of why quality and risk management are closely tied. Dave van Stein shares how to design a quality strategy, including an example.
We all know that some bugs are forgotten and stay in the backlog indefinitely. Melissa Eaden explains why it's bad and what you can do about it.
Maybe you need a Bugfixing team?