AFAIK there is no built-in way to do this.
You might want to look into macro software such as Keyboard Maestro. It allows you to switch to a certain application by hotkey and then you can select from the open windows.
Once you install Keyboard Maestro, the built-in hotkey for cycling between windows of the same application is Ctrl-Tab.
Other than that you might want to create Apple Scripts that activate a certain window and then assign hotkeys to the apple script using Keyboard Maestro. For ideas on Apple Script, look here: http://stackoverflow.com/questions/3655502/applescript-activate-window-of-a-non-scriptable-application
There appears a way to switch to a certain tab in Chrome, Firefox should not be any different: Switch between Google Chrome Tabs using AppleScript
Alternatives to KM are iKey, QuicKeys and there must be others. (KM is the one I use for Mac macros, I have no financial interest in it.)