To output HTML in Ruby On Rails you typically use Erb templates. Erb allows you to interweave Ruby and HTML code using special markup to enter Ruby code. This is similar to many other web languages out.
Sadly, I'm finding this development paradigm is a hinderence for web applications. The problem is that you're really dealing with HTML, even though you have access to Ruby. If you want to manipulate something in the HTML DOM you have to literally access the HTML DOM rather than going through abstractions. There _are_ some abstractions that handle some cases, but I think it's a problem greater than just a few missing methods.
I think what I'm after is a typical windowing toolkit like AWT, Swing, GTK, QT, etc that renders to HTML rather than the desktop screen. These things are around so I'll have to look a bit harder later.
"Markaby":http://redhanded.hobix.com/inspect/markabySMagicPermeationBranch.html is close to what I'm after. Once msgpad is out the door I may need to start adding to their code.