Using 5 (logical) lines of code
app/views/layouts/rockets.html.erb:
<head>
...
<%= javascript_include_tag 'http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js' %>
...
</head>
app/views/rockets/index.html.erb:
<%= link_to('', edit_rockets_path(@rocket), :class => 'edit', :title => 'Editing Rocket') %>
public/javascripts/application.js:
// when the dom is ready to be manipulated
$(document).ready(function ()
{
// for every <a class="edit"></a>
$('a.edit').each(function (i)
{
// make the empty anchor visible by adding some text
// <a class="edit">edit</a>
$(elem).html('edit');
});
});
Easy. 
A little fancier, still under 20 (logical) lines of code
For this example, download Shadowbox, and move it to public/shadowbox.
app/views/layouts/rockets.html.erb:
<head>
...
<%= javascript_include_tag 'http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js' %>
<%= stylesheet_link_tag '/shadowbox/shadowbox.css' %>
<%= javascript_include_tag '/shadowbox/shadowbox.js' %>
...
</head>
app/views/rockets/index.html.erb:
<%= link_to('', edit_rockets_path(@rocket), :class => 'edit', :title => 'Editing Rocket') %>
public/javascripts/application.js:
// initialize Shadowbox
Shadowbox.init({
players: [ 'iframe' ]
});
// when the dom is ready to be manipulated
$(document).ready(function ()
{
// for every <a class="edit"></a>
$('a.edit').each(function (i)
{
// make the empty anchor visible by adding some text
// <a class="edit">edit</a>
$(elem).html('edit');
// when the anchor is clicked
$(elem).click(function ()
{
// open Shadowbox
Shadowbox.open({
// load the anchor's href in an iframe
content: $(this).attr('href'),
player: 'iframe',
// set Shadowbox caption to anchor's title property
title: $(this).attr('title')
});
// stop the browser from redirecting
// to the href page (it's in the iframe already)
return false;
});
});
});