What is OS X alternative to Windows/Ubuntu hotkeys ⌘+1, ⌘+2 etc to start apps from the Dock? On Windows and Ubuntu I can use ⌘+1 to start the first app in the Dock, ⌘+2 to start the second app in the Dock, etc. How can I achieve same effect in OS X? Is it some built-in functionality or third-party extension?
You could save scripts like this somewhere in AppleScript Editor and give them shortcuts with for example Alfred or FastScripts.

tell application "System Events" to tell process "Dock"
    perform action "AXPress" of UI element 5 of list 1
end tell


(Just assigning fixed shortcuts for each application would probably be a better option though.)