You can list cookies for current domain:

function listCookies() {

    var theCookies = document.cookie.split(';');

    var aString = '';

    for (var i = 1 ; i <= theCookies.length; i++) {

        aString += i + ' ' + theCookies[i-1] + n;

    }

    return aString;

}

But you cannot list cookies for other domains for security reasons