You can also tweak the behavior of readline (for Bash and other applications) and custom make your own key combinations by editing your ~/.inputrc file. A random example from mine:

    # Insert double quotes & set cursor between them
    "\C-x\"": "\"\"\eb"
    #
    # Insert single quotes & set cursor between them
    "\C-x'": "''\eb"

See also the Bash manual:

http://www.gnu.org/software/bash/manual/bashref.html#Command...