If you don't want to display the top categories, you can use that space for your links. Edit the file includes/templates/template_default/templates/tpl_modules_catregories_tabs.php
and put in the code
Code:
<?php
if (CATEGORIES_TABS_STATUS == '1') { ?>
<div id="navCatTabsWrapper">
<div id="navCatTabs">
<style type="text/css">
#zUL,#zUL ul {padding:0;margin:0}
#zUL li ul a {margin-left:1em}
#zUL li {
float:left;
width:9em;
position:relative;
list-style-type:none;
font-weight:600
}
#zUL li ul {
visibility:hidden;
position:absolute
}
fieldset p {clear:left}
#zUL li:hover ul {
visibility:visible;
background-color:#fff;
}
</style>
<ul id="zUL">
<li><a href="#">1st Set of Links</a>
<ul>
<li><a href="Link 11">Link 1.1</a></li>
<li><a href="Link 12">Link 1.2</a></li>
<li><a href="Link 13">Link 1.3</a></li>
</ul>
</li>
<li><a href="#">2nd Set of Links</a>
<ul>
<li><a href="Link 21">Link 2.1</a></li>
<li><a href="Link 22">Link 2.2</a></li>
<li><a href="Link 23">Link 2.3</a></li>
<li><a href="Link 24">Link 2.4</a></li>
<li><a href="Link 25">Link 2.5</a></li>
</ul>
</li>
</ul>
</div>
</div>
<?php } ?>
You will maybe need to edit the spacing a bit.