If you want to open the (existing) pages in a popup window when a selection is made you can use code like this:
<apex:page>
<apex:form>
<apex:selectList size="1" onchange="selectChange(this);">
<apex:selectOption itemLabel="--None--" itemValue=""/>
<apex:selectOption itemLabel="ABC" itemValue="/apex/A?id=123"/>
<apex:selectOption itemLabel="XYZ" itemValue="/apex/A?id=456"/>
</apex:selectList>
</apex:form>
<script>
function selectChange(select) {
window.open(select.value, '_blank');
}
</script>
</apex:page>
where instead of the above hard coded apex:selectOption
s you would create then in your apex:repeat
loop.