Is it possible to set custom shortcut keys for finder, for example at the moment we have CMD+Shift+A to go to Applications, could finder be programmed to CMD+Shift+S for sites for example?
I believe the only way to do this is by using a third party utility. You will need an app where you can assign an applescript to a shortcut. A few examples of these apps :
You would then create an Applescript/Bash script that will open that folder and assign the shortcut to run that script.