Nothing revolutionary here. Just the result of some goofing around with CSS.
Give it a spin at TiddlyWiki.com.
<style>
.ch1 div {display:none;}
.ch1:hover {background-color:#F5F5F5;border:1px solid gray;}
.ch1:hover div {display:block;}
</style>
<$list filter="[tag[Articles]]">
<div class="ch1">
{{!!title}}<br>
<div style="max-height:100px;overflow:auto;">
<$transclude mode="block">
</div>
</div>
</$list>
```