I use action a lot - some I've downloaded, and some I've recorded myself.
All the frames/mounts you see on my images posted in my gallery are generated through actions.
Another one I use a lot is to convert my finished post processed image ready for posting on the web. When post processing I work with the full resolution multi layer image in 16 bit Adobe RGB. Before posting I need to duplicate (so I don't loose the option to revisit my work) resize, flatten, convert to 8 bit & convert to sRGB - ideal process for an action
