Here is a little jQuery gem I was able to figure out.

$(".outerDiv").hover(
function(){ $(this).find(".innerDiv").show(); },
function(){ $(this).find(".innerDiv").hide(); }
);

What the above code does is show <div class="innerDiv"></div> when <div class="outerDiv"></div> is hovered, and return the innerDiv to a hidden state when the the hover is lost.

I found this useful to show edit and delete links when a user hovered over a particular database item.