<div class="kutu">
    <div class="baslik">başlık</div>
    <ul class="gizli">
        <li><a href="#">link1</a></li>
        <li><a href="#">link2</a></li>
        <li><a href="#">link3</a></li>
    </ul>
</div>
<div class="kutu">
    <div class="baslik">başlık</div>
    <ul class="gizli">
        <li><a href="#">link1</a></li>
        <li><a href="#">link2</a></li>
        <li><a href="#">link3</a></li>
    </ul>
</div>

.kutu { float:left; width:200px; margin:5px; background: #e9e9e9; }

.baslik { padding:10px; }

.gizli {
    display: none;
}
.kutu:hover .gizli {
    display:block;
}