Google has announced some free open source webfonts. They currently provide only a small library of Fonts but even these can add an extra dimension to your Cappuccino app.
Simply add the necessary
link tags to your header in
index-debug.html to add the desired font, e.g.
<link rel="stylesheet" type="text/css" href="http://fonts.googleapis.com/css?family=Lobster">
fontWithName:size: and you are away!
[label setFont:[CPFont fontWithName:'Lobster' size:28]];