<select onchange="t.value=this.value">
<option value="111">111</option>
<option value="222">222</option>
<option value="333">333</option>
<option value="444">444</option>
<option value="555">555</option>
<option value="666">666</option>
</select>
<input name="t">
<option value="111">111</option>
<option value="222">222</option>
<option value="333">333</option>
<option value="444">444</option>
<option value="555">555</option>
<option value="666">666</option>
</select>
<input name="t">
<input type="checkbox" name="chk" value="2" onclick="setValue();">
<input type="checkbox" name="chk" value="3" onclick="setValue();">
<input type="checkbox" name="chk" value="4" onclick="setValue();">
<input type="checkbox" name="chk" value="5" onclick="setValue();">
<input type="text" id="t">function setValue(){
var s = "";
var chks = document.getElementsByName("chk");
for(var i=0;i<chks.length;i++){
if(chks[i].checked)
s += "," + chks[i].value;
}
if(s!=""){
s = s.substring(1);
}
document.getElementById("t").value = s;
}