Articles: Layer Masks
The right way to approach adjustment layer masks
So many people do it the long and difficult way.
Some layer mask tricks
Some handy time-savers for your Photoshop workflow.
The role of masks when cloning
The Clone Tool and layer masks go hand-in-hand.
Luminosity selections
Make a mask based on the brightness of the tones in your image.
"Extract then copy" vs "Copy then extract"
When making composites, don't do it in the wrong order.