New Post: Using SPFilterDropdown in a self referencing lookup

That's, odd, myreferences to jQuery and SPServices seem to be correct and pull down both correctly:

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js" type="text/javascript"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery.SPServices/0.7.2/jquery.SPServices-0.7.2.min.js" type="text/javascript"></script>

Your suggested alert to retrieve the current site also runs perfectly: alert($().SPServices.SPGetCurrentSite());