(Skip to 8minutes into the video for the new tools)
I have been using Photoshop CS5 at home for a while but I have recently been upgraded to it at work and using it every day has allowed me to notice some of the new tools I hadn’t seen before. This Mask tab in Photoshop CS4+ is amazing- it allows you to make non-destructive changes to your layer masks quickly and easily. I use masks for most of my work so this has been a revelation to my workflow. Enjoy!