Q: Get value from multiple dropdown list I have multiple dropdown menus that are the same, I need them to be the same.
 <select name="Obrojgoluba" id="otacmajka" class="selectbox_dodajpostojeceg" onchange="dodajpostojeceg('otac')">
  <option value="1">06557-07-681</option>
  <option value="2">07216-05-552</option>
</select>

This is my jQuery function to get value from that select list
function dodajpostojeceg(x)
{
    var ID = $('select[name="Obrojgoluba"]').val();
    alert(ID);

}

But problem is that it gets value from the first select list, not from others I have on my site. When I click on the first one it gets good values. but when I click on other select list on my site that are the same as first one it returns or empty or value it remembered from the first select list

A: You are using this
var ID = $('select[name="Obrojgoluba"]').val();

And it is possible as you said that there are multiple select on your page. So if they are having same name, above code would select the first one and that is what you are getting.
So you can just change the function and markup to made this code workable. 
function dodajpostojeceg(element)
{
    var ID = $(element).val();
    alert(ID);
}

and call this function as like this
<select name="Obrojgoluba" id="otacmajka" class="selectbox_dodajpostojeceg" onchange="dodajpostojeceg(this)">

JS Fiddle Demo

A: A strange thing to be doing, but try this:
function dodajpostojeceg(x)
{
    var ID = $(this).val();
    alert(ID);
}

As CBRoe comments, multiple identical IDs are invalid, and this may hamper your progress...

A: Make sure that the jquery lib is included and the function is defined before the html
<head>
    function dodajpostojeceg(x)
    {
        var ID = $('select[name="Obrojgoluba"]').val();
        alert(ID);
    }
</head>

<body>
    <select name="Obrojgoluba" id="otacmajka" class="selectbox_dodajpostojeceg" onchange="dodajpostojeceg('otac')">
        <option value="1">06557-07-681</option>
        <option value="2">07216-05-552</option>
    </select>
</body>

Fiddle: http://jsfiddle.net/kR8yH/
When the html is rendered, it will look for a function named dodajpostojeceg() and if it not defined, it will not be able to bind the select and the function
I am assuming that all the selects are uniquely named
