Here's a couple more that I forgot that are also useful...
While in the brush tool...
Shift + Right Click = Quick blending options
Also in the brush tool...
Ctrl + Right Click = Toggle Layers (This is why it's handy to name layers).
Also, this is handy if you go through layers quickly like I do while sketching (when I'm madly doodling, I don't bother to create new documents when moving from sketch to sketch; I just create new layers and hide the old ones).
Ctrl + Shift + N = New Layer